Any large, simple stone or pebble tool with a single, transverse cutting edge. It was used for hacking, breaking, or chopping and was especially characteristic of Middle Pleistocene, pre-Acheulian industries of the Old World, such as Choukoutien, in the Clactonian in England, and at the earliest levels of Oldowan industries. This crude tool was made by striking a limited number of flakes from the edge of a cobble or fist-size rock to produce a coarse cutting edge. It persisted until the Neolithic.