A large number of NUHOC members are climbers.
Metrorock rock gym is a favorite, and is easily accessed from the Orange Line. They even provide a shuttle service from the Wellington stop if you phone them.
Before reading further, please read the DISCLAIMER about rock climbing. If you don't want to, heres a quick synopsis: Climbing can be amazingly dangerous if you don't understand what you're getting yourself into. ALWAYS travel with either a guide, or someone who knows what they are doing, and preferably seek professional training before embarking on your own. Live by the mantra of climbers everywhere: "Don't fuck up and die"
Basic info on climbing
In the beginning, there were mountains. Then, some men saw those mountains and decided that, should they somehow find a way to the top of them, women would find them more attractive than the other men in the area. Thus, Mountaineering was born. As the French, German and English were scaling the Alps of Europe, mountaineers set their sights on harder and harder routes, which began to require highly technical skills. To hone these skills the mountaineers would practice the climbing moves at small ledges, or crags, around their home towns, beginning the sport of pure rock climbing: the attempt to climb harder and constantly more challenging rock faces.
There are two basic types of climbing out there, FREE climbing and AID climbing.
Free climbing is what NUHOC primarily does. While free climbing, the climber is held onto the rock only by their own hands and feet, and their will to not let gravity take over. The climber is generally protected from a potentially devastating fall by a rope and harness attached to their person, so that if they fall the rope will (hopefully) catch them before they hit the ground. Free climbing can be further broken down into four sub-classifications:
This is climbing at its most basic: there is a climber, a rock, and no extra equipment besides the possibility of shoes and a pad (crash pad) to protect them from a nasty landing. While bouldering most climbers stay at heights below 15 feet, though there are some "highball" routes that can extend much higher. Due to the short nature of many bouldering routes, they are generally considered to be at least slightly more strenuous on a climber than a equivalent roped climb, thus leading to the phrase, "bouldery moves" on a climb.
Bouldering problems are rated on a "V" scale with no upper limit, starting at V0- and moving upwards of V16
Top-roped climbing is where the climber is attached to a rope via a harness, and is "belayed" by a partner. The rope is anchored at the top of the intended climb (hence the name top-rope), and as the climber ascends the rock face their partner pulls in the slack, or belays their climber. This type of climbing is a moderately gear-intensive style of climbing (more intensive than bouldering, but less intensive than sport leading, and FAR less intensive than Trad leading or aid) due to the fact that both climbing partners need a harness, shoes, a rope, and some form of anchor at the top of the climb. In general when climbing on top-rope, the first climber will begin climbing, and when they reach the top the belayer will then lower the climber back to the ground, and the partners will switch.
Anchors are generally made off of large static objects at the top of the climb, and there are many ways to make a solid anchor. As with most aspects of climbing, there are many places to learn about how to set up safe systems, so its a good idea to take some time to review before heading out on your own.
Lead climbing differs from top-roped and bouldering in a very distinct way; instead of having the anchor held statically at the top of the climb, the climber (or "Leader" in this type of climbing) is constantly moving the anchor up the wall, starting at the bottom. To do this, the rope is connected directly from the belayer to the leader, and as the leader climbs they "clips in" to protection strategically spaced along the wall. By clipping in, the point they clip to now becomes their anchor, and should they fall as they climb above it, the fall is limited to a little over twice the distance that they are above their last piece of protection.
Sport Climbing is when the leader clips into Bolts pre-emplaced into the rock wall. These bolts allow the climber to carry small amounts of gear (typically two Carabiners connected together, known as "Quick Draws"), and climb light and quick.
Traditional (Trad) Climbing is where there are few or no bolts already placed on the wall, and the leader is required to bring along extra gear that they can use to attach to the rock as protection. Cams, Nuts, Tri-Cams, and Hex's are all examples of "Trad gear", or pieces of protection used to anchor a Trad Climber onto the rock.
Lead climbing can also be extended into multiple concurrent climbs, or "multi-pitch" climbs. These climbs consist of anywhere from two to fifty "pitches" of climbing, where the leader will climb up to a full rope-length upwards, build a full anchor, and then the belayer will climb up to the original leader, after which they will continue this cycle until the summit is gained. El Cap in Yosemite is considered one of the most classic "big wall" multi-pitch climb, but there are many smaller two or three pitch climbs all over the country, and all over the world.