I'm participating in a bushcraft skill challenge over on Blade Forums. Every day this month I will make a figure four deadfall trap. So far I've made one each day for a week, with all but one being successful. The carving demands are very basic. The figure four consists of three sticks and a heavy weight such as a rock or log. The three sticks are cut and notched, then set together under the heavy object. All four parts support each other. The weight rests on the diagonal (lever) stick, which pivots on the upright, and the lever pulls on the trigger stick, which is notched and rests against the upright. When the trigger stick is disturbed, the trap collapses and the deadfall crushes the target animal.
By the end of October this should be a well honed skill.