A top-bar hive has bars from which the honey bees attach and hang wax comb, an array of hexagonal (six sided) cells. Unlike the full four-sided frames used in a Langstroth hive, the comb on bars cannot be centrifuged to extract honey and then reused. This characteristic might lead to a lower production of honey, but the honey from clear yellow comb (comb that has not been used for brood) is of the highest quality and can be used as in-comb honey product, highly prized by some users in preference to liquid honey. This may be spread on hot toast, melting the wax, or may be chewed as a treat, releasing the honey.
A beekeeper can make top bars from any plain wood. The top bars are usually 1¼ inches to 1⅜ inches (32–35 mm) wide, depending on local conditions and the type of bee to be housed. Combs can be handled individually. The depth of the bar and the length of the bar can be whatever the beekeeper wants, but usually between 17″ and 20″. The hive body can be a long box, covered by a series of top bars laid side by side like a wooden keys of a marimba. The depth of the top bar hive should be 12″ or less. If deeper, the weight of the comb filled with honey tends to cause it to fall off the bar into the bottom of the hive. The bees will lose access to this during the winter cluster in the hanging combs, thus increasing their likelihood of starving.
It is important to give the bees a clear starting point to build comb on each top bar. Some TBH beekeepers fashion their top bars with a V-shaped bottom to guide the comb building. Alternatively, some use a table saw to cut two closely spaced slots along the long axis of each new top bar. Either type of guide, wax line or grooves, gives bees a place to hold on to with their hooked feet. This allows a substantial “drape” of bees to form, which is always the beginning of comb building.
(There are many other variations of this same idea: for example, some beekeepers cut a single thin groove, then firmly glue a Popsicle stick or a thin slat of balsa wood into it with wood glue, thus creating a slightly protruding piece upon which the bees begin their building.)
Unlike the conventional Langstroth hives, the entrance is not part of the hive’s ventilation system. This allows a great deal of flexibility in both placement and configuration.
The provision of a single entrance with a landing platform at one end will help in restricting the placement of pollen stores. Combs with pollen will tend to be in the first two combs nearest the entrance. A single entrance is also more defensible and enables the bees to combat robbing by bees from other colonies. This entrance should be protected by some sort of canopy (or an extension of the roof) to reduce or eliminate the formation of dew on the landing platform — large drops of water will tend to trap early leaving bees until the water evaporates.
The entrance should not be placed high on the hive as this will allow the escape of winter heat. Rather than place the entrance in the end wall it should be located in one of the sides of the hive, especially in the Tanzanian (straight sided) hive. This will allow the bees to access the side which they must use to access comb in the back of the hive for storing nectar.
One very effective entrance configuration is to provide a landing pad, which is an extension of a covered porch for the guard bees. All bees are prevented from flying directly into the hive by making the entrance a number of 5/16 inch (8 mm) holes in the hive end wall. Thus any bee entering the hive must land on the pad, cross the sheltered porch and walk through one of the several entrance holes. The guard bees on the sheltered porch may here inspect and communicate with the arrivals and so reject any raiders, which are recognized by not carrying food and by carrying scents from a foreign hive.
(Of course, some beekeepers instead advocate placing several small entrance openings at the top, at one end of the hive only and not of sufficient size to allow significant loss of heat, with or without landing platforms.)