Yawl

A yawl (from Dutch Jolt) is a two-misted sailing craft similar to a sloop or cutter but with an extra mizzen mast well behind of the main mast, often right on the transom. A small mizzen sail is raise on the mizzen mast.
The yawl is often puzzled with the ketch, which also has two masts with the main mast foremost. The common view is that a ketch has the mizzen mast forward of the rudder post whereas the mizzen on a yawl is aft of the wheel post. This definition is a relatively recent meaning and the historical definition is likely to be quite different.
In practice, on a ketch the main purpose of the mizzen mast is to help push the vessel, while on a yawl it is mostly used for the purposes of trim and balance. In result the mizzen sail of a yawl tends to be smaller, and the mainsail larger, when compared to a ketch of similar size. The mainsail of a yawl will be comparable in size to that of a similarly sized and proportioned sloop.
The yawl was initially developed as a rig for commercial fishing boats, one good example of this being the Sercombe Yawl (a traditional small fishing boat built in Devon). In its heyday, the rig was mainly popular with single-handed sailors, such as circumnavigators Joshua Slocum and Francis Chi Chester. This was mostly due to the remarkable ability of a yawl to be trimmed to follow a compass course exactly despite minor wind shifts. Modern self-steering and navigation aids have made this less important, and the yawl has normally fallen out of favor.