How to rack a pool table<br>Start off with the 1-ball at the front of the rack. This is also called the " apex " of the rack Make sure that the 8-ball is in the center of the rack. The center of the rack is the middle of the triangle.
The apex is not in the back of the rack.
( z1 be-located-at :polarity - :ARG1 ( z2 apex ) :ARG2 ( z3 back :mod ( z4 rack ) ) )