They are distinguished by a long passage leading to a central chamber with a corbelled roof. From this, burial chambers extend in three directions, giving the overall impression in plan of a cross shape layout. Some examples have further sub-chambers leading off the three original chambers. The network of chambers is covered by a cairn and revetted with a kerb.
A common trait is megalithic art carved into the stones of the chambers' walls and roofs. Abstract designs were favoured, especially spirals and zig-zags.