Frames hang in the hive bodies and honey supers like files in a file cabinet. Foundation is inserted into the frames for the bees to build cells on. Most frames are standard and are usually offered in two types. The first has a grooved top and bottom rail that plastic and thicker wax foundation slips into. The second has a grooved bottom rial but the top rail has a removable wedge in the top rail. The foundation is slipped into the bottom groove and laid against the ridge on the bottom side of the top rail. The wedge is put in place and nailed. Either frame type works well, it seems it is a matter of preferance.