A drop of zone is a feature unique to Antweight arenas. It is essentially a trench around the sides of the arena, which because 50% of the arena side must be open with no wall, robots can be pushed out into. If a robot is pushed out, it is declared the loser of the fight.
As of version 4.0 of the Antweight World Series Rules, the drop of zone must comply with the following conditions:
This is so even the largest Antweights can fit into the ditch.