A low‐tech technique for locating buried ditches and pits at sites with a solid underlying natural bedrock (e.g. chalk or limestone) and relatively thin stratigraphy. The procedure is to place a block of wood on the ground surface and then hit it hard with a sledge‐hammer. A dull thud will be heard where there are disturbances in the bedrock while a sharper ring is emitted where undisturbed bedrock lies below the topsoil. By systematically working across a site and mapping the sounds, the distribution and extent of bedrock cut features can be worked out.