Use on strong hives, put on a weak colony and you could start robbing. The same effect can be achieved by shifting the supers ahead to leave a bee entrance or by putting a stick or small rocks so it tilts the supers leaving a bee space entrance. I have done this on strong hives in the past when I come across them. I find it easier to use a piece of stick or rocks rather than carry extra equipment.
Those entrances work well and are good when doing stacked 2 queen hives for the top queen and brood nest.
