This can be used like:
tether_box = box() -- needs to be default in this case
-- calculate minimum AA box from four corners of room
-- can be as many corners as needed to make easy for geometry of room,
-- but at least 3 would be required
tether_box:add(831.11, -16.90)
tether_box:add(752.95, -16.90)
tether_box:add(752.90, -159.11)
tether_box:add(831.10, -159.11)