The Horizontal top bar hive was developed as a lower-cost alternative to the standard Framed hives and equipment. They are becoming very popular in the UK due to their alignment with the organic, treatment-free philosophies of many new beekeeping devotees. They are also popular, owing to their simplicity and low cost, in developing countries. Top-bar hives have movable comb and make use of the concept of bee space.
The top-bar hive is so named because the bees draw their comb from a top bar suspended across the top of a cavity and not inside a full rectangular frame with sides and a bottom bar. The beekeeper does not provide foundation wax for the bees to build from. The bees build the comb so it hangs down from the top bar. This is in keeping with the way bees build wax in a natural cavity.
The hive body of a common style of top-bar hive is often shaped as an inverted trapezoid. Unlike the Langstroth design, this style of top-bar hive is expanded horizontally, not vertically. The top-bar design is a single, much longer box, with the bars hanging in parallel. This common style is sometimes referred to as a horizontal Top Bar hive.
Because top bars are used as opposed to frames, the honey is usually extracted by crushing and straining. Because the bees have to rebuild their comb after honey is harvested, a top-bar hive yields a beeswax harvest in addition to honey. The bees store most of their honey separately from the areas where they are raising the brood.