Make sure you leave enough room to fit a wrench in the hole if you are not using the allen type wrenches. You can use the cardboard from 12 packs of soda to make the mold box. This is the trickiest part of making holds. Otherwise, you will get ridges after it cures that turn into VERY sharp features when you pour your hold. So, make sure to force the silicon in.
Some suggestions are to let the tubes of silicon sit in hot water before pouring the silicon.
Or, mix the silicon in mineral spirits to make it more liquidy. Let the mold set for about one week. When it's done setting, cut the foam block out from the bottom of the box and whola, you have a mold. The picture above shows a pinch, a hold with features on the outside as well as a three finger and one finger pocket, and a set of three jibs for feet. Notice that there is a stem where your bolt hole will be or screw holes for the jibs.