Depending on the kind of rock and the location, the trad climber will need a different mix of climbing gear. This page focuses on what's needed for a 'typical' traditional multi-pitch rock climb, if such a thing exists.
Good for any roped outdoor climbing. Especially essential for trad multi-pitch. A helmet keeps the climbers brain safe. Multi-pitch routes are longer by definition, therefore have more chance of loose rock. Even a modest size rock, dropped from enough height can kill, so the climber should make sure they have a helmet to give them a better chance. It should be worn when belaying and even on approach to the crag if the path follows the base of the cliff bringing in the risk of loose rocks falling or being dislodged by other climbers. A helmet can also reduce the impact of a headfirst fall into rock. This can happen in various scenarios, especially when the leader has their leg between the rock and rope, meaning they are more likely to invert when falling.
Double Ropes
Most of the time, climbers use a pair of double ropes for trad multi-pitch climbing. Sometimes also called half ropes, they help reduce rope drag (the zig zag that increases friction when leading) that comes from winding routes, or gear placements that are spread out either side on a straight route. Double ropes are a little thinner than single ropes (which are mainly used for short routes & sport climbs). The trade off here, is they weigh less but are also generally less durable so not designed to take as many falls as a thicker sport single rope. They also always have to be used in a pair. A climber should never lead on just a single rope from a pair of half ropes. They are not tested to hold such a high fall factor. As rope technology has advanced you can now also buy triple rated ropes. Unlike half / double ropes, they are both light weight and can be used as a single strand for leading. They tend to be more expensive though.
Harness
Whilst there are specific harnesses designed for trad climbing, the main factors are comfort, weight, number and size of gear loops and the buckle system. Most new harness have a self-locking buckle meaning they are less likely to come loose. For trad, the climber will want at least 4 decent sized gear loops to help carry protection and quickdraws. 5 is a good number especially for multi-pitch, where spare or emergency pieces can be helpful. Some harnesses have 7 loops. This can actually be less helpful because it's awkward to find the gear needed when there are so many overlapping loops. Lighter is generally better but it can be a mistake to sacrifice on comfort, for trad multi-pitch. This is because the climber will need to have their harness on for hours, often with many kilos of gear on it. Therefore, padding is helpful.
Belay Device
Every year climbing companies release new and varied belay devices. Belay devices fall into two broad categories of solid vs mechanical/assisted. All devices work by increasing friction on the rope making it easier to catch and hold a falling climber, but some 'assisted' devices like the grigi go as far as to (mostly) automatically lock in the event of a fall. The range of choice can seem confusing, but there are clear pros and cons to the options. An assisted device is typically much more expensive to buy, weights more and are usually only usable with a single rope. The advantage is that they automatically lock (some exceptions) which is helpful if the belayer has a lapse of concentration. This is typically used for sport climbing but can be used for trad climbing on a single strand of rope. A static 'tube' device has the advantage of being cheap, light, and usually designed to take 2 ropes. Some devices are also designed specifically for multi-pitch and have an option to belay from above in 'guide mode'. The petzl Reverso or DMM pivot are two good examples. This means the belayer can attach the device to the anchor rather than belay from the harness when bringing up a second. The advantages here are comfort of belaying, plus the fact the device will (mostly) automatically lock if the second falls. This is ideal for bringing up two climbers together where both falling would be a problem to hold the weight on the harness. The downside here is complexity of set up and the need to change the belay system when 'swinging leads' ie the second then leads the next pitch. Additionally there are other ways to belay (plate, eight or hitch etc), which typically don't have any major advantages over a tube device.
Head Torch
Most of the time the climber won't need a head torch, but if it gets dark during the climb or in the middle of a decent, the climber will be glad for having it. In these situations, the options are to continue with a headtorch or face benightment while waiting for the morning sun. It can be easier to get lost than it may seem. To replay a chain of events from January 2018, myself and a party of 3 got lost navigating to Roca Gris in Span. When this happend, it meant we started climbing just an hour late, we also moved slower than expected and then took a while to find the abseil anchor. The days were still short and it was pitch black on the third and final abseil. If I didn't have a head torch the three or us might have been benighted hanging from 2 bolts on a sheer face.
Personal Anchor
A personal anchor system or PAS can be pretty handy on long multi-pitch climbs. Climbers can do without one if they use the rope to build the anchor or if they use a sling to make a 'master point' to clip directly to the harness. However, a personal anchor can make it easy to take a break at a belay point, especially when leading in blocks, or climbing as a group of 3. A dedicated PAS can also be used to help attach to a pair of bolts quickly. In addition, it can also be used to extend an abseil device further off the hardness. A PAS also allows quick adjustment of position Vs a lanyard or sling.
Nuts and Wires
The backbone of traditional protection are nuts, sometimes called wires. These are metal lumps on the end of a metal wire loop, and come in many shapes and sizes. They can be slotted, threaded and generally wedged into cracks, gaps or slots in rock, in such a way that they can catch a fall. There are 3 main factors to a climbing nut. Shape, size and metal type. These three factors also influence weight and strengths. For example, small micro-wires weight very little but are also not as strong as larger nuts. In terms of shape, nuts can be 'offset' to fit better into flaring cracks or more uniform in shape. Most nuts are designed to be used in a few orientations, i.e. they have a thin and thick side and usually also curve one way or the other. This makes them more versatile. Size is an obvious factor. Bigger nuts are for bigger gaps. Most trad routes call for a rack of at least 10 different sized nuts. For most multi-pitch climbs, it's not un-common to take 20+ nuts / wires. The final factor is the metal the nut is made from. Softer metals like brass, are used for smaller nuts. They deform into the rock when catching a fall, thus increasing the friction and stopping power. Small brass alloy wires are often called RPs after their inventor Roland Pauligk. More recently, brands have made half nuts which are full size but have reduced profile and weight.
Quickdraws
Two karabiners attached together with sewn sling make a quickdraw. One side clips protection the other clips the rope. These are a simple and essential piece of climbing gear. Quickdraws tend to be designed for either sport climbing or trad. Sport 'draws' generally have a short sewn sling that is thicker and therefore more durable, as well as thicker karabiners. The trade-off here is durability vs weight. Trad quickdraws tend to have a thinner sling and, are almost always wire gate carabineers to save weight. In addition, a longer sling will help reduce rope drag and the impact force on the gear, as well as reduce the chance of the gear pulling out when climbing above it. As a result, some climbers only carry long (25cm+) quickdraws for trad. But the trade-off here is a slightly bigger fall. There are a few companies that make ultra-light carabineers like the Petzl Ange or Edelrid 19g, which, as the name suggests, weighs only 19 grams, these make ulta-light quickdraws.
Alpine Draws
Like quickdraws, alpine draws follow the same format but are more versatile. They use a non-sewn sling that's usually 60cm long. This allows the climber to extend the 'runner' quite far if needed. Alternativly the draw can be doubled and made 30cm or used at one third length of 20cm. This shortened form, is usually how it's clipped to the harness. To do this, both carabineers are clipped to the 60cm open sling, one carabineer is then passed though the middle of the other and clipped back to the sling in the middle after its passed through. A multi-pitch rack for climbing 45m+ pitches will generally need around 12 draws. x8 normal 25cm draws and x4 60cm alpine draws is not a bad place to start. If the route relies on wires more than cams, more draws may be needed. Also some experienced climbers recommend more alpine draws over normal draws, due to their flexibility. A climber can also use an alpine draw as protection in itself, by threading certain pockets or slinging rock spikes or even trees. However it's important to be careful the sling won't lift off the spike or the tree won't lift off the crag, in the event of a fall.
Cams
Cams are another main component of a good climbing rack. Many routes can be climbed with just nuts for example the limestone at Avon, but for anything with lots of parallel sided cracks, like Granite in the Mournes, then cams are essential. The main advantage of a cam is its ability to protect parallel sided cracks as well as pockets. Each cam has a range it can protect, this means it's easier and quicker to get a cam into many of the normal placements a nut can protect. But before ditching all the nuts on a trad rack, it's helpful to be aware that there are number of significant downsides to cams. Firstly they are much heavier than passive protection. A set of 10 cams will weight much more than 10 nuts. In addition cams are considerably more expensive. A cam is typically 5 times the price of a nut. Cams also exert a lot of force on the rock, meaning they can break the rock and fail in certain placements like flakes, which otherwise may not break if a nut was used. Cams can also 'walk' deeper into some cracks making them hard to get out later. Durability is another major draw back. Personally I have retired 5 cams from 3 different manufacturers in the last two years. I have still have and use all the original nuts I brought 10 years ago (apart from one that was accidentally dropped and lost down Cwm Idwal slabs). None of the cams I retired took a fall. One had a lobe pop off when I took it off my harness. Three had a retaining ring errode and the heads mis-align. One broke a wire and spring. A final positive consideration for cams, is that they can hold their position better than nuts in some instances. A nut will have gravity pull it one way and the rope shake and loosen it in another direction, cams however actively grip the rock, reducing this.
Locking Carabineers
Locking carabineers are an essential part of any traditional climbing rack. They are typically used for key parts of the multi-pitch climbing system like the belay and anchors. There are a few types of locking carabineer. The original and generally more common is the screwgate. This has a collar which is spun round and screwed up over the join, in order to lock the gate closed. Some carabineers use twist lock sleeves which are essentially sprung closed. These require a pull and twist to unlock. The advantage is they tend to automatically lock but can still be undone quickly. More recently Grivel have released their twin gate carabineers. These have two opposing gates meaning they can't be opened by just pushing on the gate (in either direction), however they are still quick and easy to open once a climber has mastered the knack of it. These make a very light and secure carabineer.
Slings & Cordlets
Slings & cordletts have many very useful applications for trad multi pitch climbing. A common use is to equalise multiple placements at an anchor point, to create an robust single connection point. Most trad gear can take a decent impact force from a climber fall, however, smaller gear is often weaker and rock could have unseen fractures or hollowness that makes it more fragile than it initially appears, therefore reducing the impact on a placement is always a good idea. A great way to do that at an anchor is to equalise the load over multiple pieces of gear. Typically, a climber would make three or more good placements and equalise them together using a single large sling or multiple smaller slings. The rope can also be used to build an anchor, but if the party is leading in blocks rather than swinging leads, it may be better to create a master point (or Power Point) using a large sling. Whole sections of books (like High) have been written just on this subject alone. The other key use of slings is as protection. Large rock spikes, flakes or wedged boulders can have slings passed around them so the rock will catch a fall. The level of protection provided by this method ranges from marginal on shallow spikes to 'bomber' i.e. very robust, on wedged boulders where the sling has no way to come out once clipped. Slings can also be used to extend protection to reduce rope drag.
Chalk & Chalk Bag
Chalk is often not needed on easy mountain routes. However on hard routes, routes in hot climates or wet rock it can be essential to success. Nowadays there are lots of types of chalk. Eco chalk is worth a special mention as it bio-degrades quicker and leaves less marks on the rock when outdoors. Eco Chalk is sometimes the only accepted chalk at some crags, usually smaller sandstone walls. For most mountain crags the build up of chalk is not too much of an issue. Every climber has a preference on chalk. Cheap chalk is often more or less identical to expensive branded chalk. Different chalk bags have some clearer pros and cons thou. Small and light is handy to save weight. Chalk bags with pockets and pouches can be used for handy storage on a multi-pitch climb. Things like a knife, back up prussik, hand tape, first aid or even snacks can be carried in chalk bag zip pockets. It's worth adding that a bag attached with a strap or cordlett is better than with a carabineer, in case the climber needs to bring the bag round to the front or side in order to chalk up.
Abseil Device / Back Up Belay
When on a mountain route, it's good to have a back up belay device or abseil device that could be used to belay in an emergency. The advantage of a dedicated figure 8 style abseil device, is the speed and smoothness of the abseil experience. However, the disadvantage is the aditional weight.
Tri-Cams
Tri-cams offer some strong advantages over both nuts and cams on paper. In addition, there are some places where nothing but a tri-cam will fit. That said they have some significant disadvantages that mean they remain a niche piece of gear for many climbers. They work by wedging the spike, usually point down, in a crack or pocket with the sling running down over the back of the tri-cam between the other 2 metal ribs. This creates three points of contact with the rock (Tri) and will generate a camming (cam) motion when they catch a fall, hence the name. The key advantages are: they are cheaper than cams (although more expensive than nuts), they have a narrow head making them work in small pockets. The spike also means they can work in odd shaped placements because only one small part of the rock needs a viable surface. They can also be used passively like a nut. However, their downsides are many. They are fiddly and slower to place, even once you have got used to them. They also have a tendency to get stuck in a way that means they are unlikely to catch a fall, but also hard to correct or remove. A nut key is almost always essential to removing them, and sometimes even placing them. There is also a risk they tip over if not placed and loaded correctly, making them marginal where a cam might be better.
Ball-nuts
Sometimes called sliders, ball nuts are a single nut with a sliding surface on one side, meaning the nut essentially, expands slightly and therefore holds better. The one key strength is, the protection is partially active and so can hold better than a normal nut but, but can have a much smaller profile than a cam. It's a niche middle ground piece of gear, more commonly used for aid climbing, however it can provide some extra options on a trad rack, especially on very hard routes with ultra thin cracks.
Sky Hooks
A sky hook is a small metal hook with a sling or cord. It can be used to hook over flakes, ledges or even placed in small pockets. It's primarily used for aid climbing, however it can also offer very marginal protection (i.e. more psychological confidence, than physical protection) in certain circumstances. Whilst certainly not a key piece in a trad rack, it can be deployed in an emergency, especially on slabby routes with limited features.
Prussik Cord
Usually 5 or 6mm in diameter, specialist cord can be used to make prussiks, ideal for backing up an abseil. The cord can also be used in place of a sling in an emergency; however, it usually has much lower breaking strength than dyneema or nylon slings. It's vital the right dedicated prussik cord is used. Dyneema cord will melt with friction and other cord may not be strong enough.
Hex
A hex is, as the name suggests, a hexagonal shaped piece of metal with either, a stiff metal wire just like nuts, or a soft and flexible but strong dyneema sling built into it (nylon cord can also be used). Typically Hexes come in larger sizes than nuts and are often hollow to save weight (but are still weighty gear). It's a form of passive protection and essentially acts like a large nut. The advantage is its cheap cost and high strength. The disadvantages of hexes are the noise they make when hanging from the harness and knocking into other gear. Hex's are sometimes dubbed cow bells for this reason. In addition, a set of large hexes add significant weight, with little flexibility on placement compared to a cam. They are a useful addition to a climber’s rack if the route requires lots of larger pieces, however for most routes they are not worth the weight and noise the bring.