The clinic we offered on July 13, 2010 had three parts. The first part was a lecture / discussion session about the physics of placing pro. I started it by asking the participants to take a close look at a couple of nuts and cams of various sizes and to tell us what their strength rating is in units of kilo Newton (kN). This led us to the first talking point, “Will this piece of gear hold me?” I asked everyone to calculate their weight, due to their mass and the gravitational acceleration on Earth, in kN. The answers unanimously were numbers below 1kN, around ¾ of a kN or so. This was well below the rating of even the smallest nut we looked at (4kN). We inferred this means that you can clip directly to even the smallest piece and it will not break under the load of your weight. The next situation we considered was having a rope clipped to the piece, and the climber sitting on the piece with the belay on. This introduced the pulley effect, which doubles the force at the piece. The resulting force was still only between 1 and 2kN, well below the rating of the smallest piece of gear that I carry (but potentially above what someone else has on their rack). The conclusion we drew was that most of the pieces would be OK to hangdog on or be lowered off of with a rope. The third scenario involved falling on the piece. We first discussed why we lead climb on a dynamic rope, and how it is the stretching of the rope which cushions our impact. In response to a question I digressed a bit into of how hard it is to say whether a certain fall will kill you or not, since it depends very much on which part of your body is impacted, and on the properties of the object that you hit. To assess falling on a piece of gear, I next introduced the equation for impact force and read off some examples of the forces for varying fall factors. (I also assumed as given a UIAA standard rope that allows for a 12kN impact force for a climber weighting 80kg). This exercise demonstrated that even small fall factors can generate forces on a piece that exceed its strength rating. We discussed the implications of the fall factor on strategies for how to space out our gear after we leave the belay, and along a route.
The second talking point I had prepared was, “Will the gear hold in the rock?” I spoke a little bit about contact forces, friction, and how the load of a piece is distributed to the rock that it is sitting in. Most importantly, using a simple demonstration, we saw that when we insert a piece into rock and expect it to stay there, the rocks must have the ability to push back onto the piece without breaking. This has implications for the macro- and micro-structure of the rock that should be considered in making a gear placement. 
The second part of the clinic was “U place pro.” Everyone swarmed out with either their own racks, or mini-racks we had assembled from our gear. The cracks Sam and I had found were concentrated in two separate areas, so half the class went to the first and the other half to the second one. I asked everyone to place as many nuts and cams as possible, and to make sure to place both, nuts and cams. Some people worked alone, others worked in teams of two, and there was immediately a lot of discussion about rock quality, features, and what piece should be tried.
The last part of the clinic was the critique. For this, Sam walked around and looked at and tugged on each and every piece, told us if he would take a fall on that piece, and invited discussion about the placement and its potential
improvements from all the participants. After we had looked at all the placements, there was actually enough time to have a second round of placing pro. Participants swapped areas and we repeated the placing and critiquing steps. Sam ended up having to use a flashlight to evaluate the placements; it was quickly getting dark on this overcast summer evening.
