Just for clarification, how are you going to trigger the trap? And to clarify the trap further, the log swings down horizontally, set to hit a medium-sized character at about the mid-torso (and, naturally, miss a small character).
OOC: That was how I envisioned the trap. The rope crosses the path, and will be affixed at both ends to something to keep the rope off the ground. OH will go to the side, lie prone (if six o'clock would lie in the log's path, he'll stay this side of the trajectory, perhaps angled at 4 o'clock), and (since he's not a lock picker or whatever) try to trigger the trap (poking it with his club, or whatever seems reasonable).