What?

A top bar hive body with half of its top bars.
A top bar hive is a long, horizontal hive with removable combs. It consists of just three components:
- the hive body.
- the top bars.
- a cover.
The hive body is just a trough shaped box with enough volume for a bee's nest and the beekeeper's needs. A hole in the hive body provides a bee entrance.
Wooden bars, the top bars, mirror natural comb spacing. They set on top of the hive body covering the opening. The bees attach their comb the top bars, which can be removed for inspections and colony management.
And a cover protects the top bars and hive body from the weather.
That's it! A top bar hive is a beehive that's as simple as it gets.
Advantages

A fully operational top bar hive.
- Facilitate natural beekeeping. Bees build the broodnest their way.
- Less colony disturbance.
- Minimal beekeeper exposure.
- No heavy, repetitive lifting.
- Inexpensive. Cost $30 versus $200 for a standard hive.
- Produce the highest quality honey and wax.
- No extracting equipment needed.
- Self contained. No additional storage space required.
- Facilitate comb rotation.
- Easy to build.
- An ideal educational hive.
- An ideal urban beehive.
- Won't break apart when dropped.
- Weather tight.
- Low center of gravity. Won't tip over.
- Adaptable to local building materials, conditions, needs.
Examples
Since top bar hives cannot be purchased, they come in a myriad of styles to reflect differing beekeepers needs. Ranging from the rustic to the ornate, they've been constructed out of steel barrels, adobe, recycled water heaters, plastic food grade barrels, old refrigerators, ammunition cases, pallets, papercrete, etc.
Here are a few examples typically found in the USA. Most of them are built from conventional lumber.

A Maryland beekeeper's top bar hive.

Keith Malone.

Dennis Murrell.
Your Top bar hive?
So, what would your top bar hive look like? I bet it would be a beauty. And I know it would be the best top bar hive ever built. Because it would give you more satisfaction than any other hive. And it would be made especially for you and your needs.