Enables or disables trigger bounds.
This will give the entity a "trigger box" that extends around its bounding box by boundSize units in X/Y and (boundSize / 2) in +Z (-Z remains the same). The trigger box is world aligned and will work regardless of the object's solidity and collision group.
Valve use trigger boxes for all pickup items. Their bloat size is 24, a surprisingly large figure.
This requires developer to be set to 1.