The lid goes on top of the stack of bee boxes. Ours are a piece of plywood with two end pieces attached.
There are two main styles of lid, the migratory lid and telescoping lid. We use migratory lids. Migratory lids fit flush with the box on the sides and overhang on the front and back. This is useful when stacking boxes next to each other, like when wintering or trucking bees.
The telescoping lid fits around the whole box and has overhang on four sides. Telescoping lids require an inner cover for winter to vent moist air.
Some migratory lids, like the ones shown below, have ventilation holes cut in them for winter. This eliminates the need for an inner cover.
Bees glue down the lid with propolis so it will stay on in the wind. . . until the beekeeper breaks the propolis seal open with the hive tool to inspect the colony. Sometimes it is necessary to put a rock or other weight on top after inspecting.
Some beekeepers like fancy garden-style lids, like our invention, the Barn Hive, which acts both as lid and 5-frame box.