FENCETells the turtle to enter "fence" mode. In fence mode, when the turtle is asked to move past the boundary of the drawing surface, it moves as far as it can and then stops at the edge with an "out of bounds" error message.
Compare this command with WRAP, WINDOW, and PERSPECTIVE.
FENCE FORWARD 10000turtle out of boundsFORWARD 10turtle out of boundsBACK 500