The string on ICEBOX is fed through the hole on the pulley attached to the up and down motor, then down around the left side of the roller for the down switch, and then to the right side of the last roller which will center the string with the hole in the bottom of the assembly.
Routing the string incorrectly will cause the string to rub along the roller brackets which will cause premature wear on the string and problems with the up and down switch correctly activating.