worked, that is uncut. It could be thought that this is a mistake or an error. But often the most probable reason for this is that it was intentional. There are a large number of hand axes with an uncut base, unworked or partially cleaned ... an area has intentionally been left on these pieces as a grip, it is called the heel. This heel acts as a handle as it is easy to grip". (This hypothesis remains unproven and is not commonly used.) Hand axes with residual cortex on an edge—The whole of their edges are knapped except for a small area where the cortex remains (leaving a small area without a sharp edge). This area can be at the base, side or oblique. In all cases it is small, leaving cutting edges on both sides. Hand axes with a cutting edge around the whole circumference—The circumference is knapped to a cutting edge, although some residual areas of cortex may persist on either face, without affecting the cutting edge's effectiveness. Production Older hand axes were produced by direct percussion with a stone hammer and can be distinguished by their thickness and a sinuous border. Mousterian hand axes were produced with a soft billet of antler or wood and are much thinner, more symmetrical and have a straight border. An experienced flintknapper needs less than 15 minutes to produce a good quality hand axe. A simple hand axe can be made from a beach pebble in less than 3 minutes. The manufacturing process employs lithic reduction. This phase is commonly thought of as the most important in hand axe fabrication, although it is not always used, such as for hand axes made from flakes or a suitable tool stone. An important concern is the implement that has been used to form the biface. If multiple implements were used, it is essential to discover in what order they were used and the result obtained by each one. The most common implements are: Hard hammer faces Hand axes can be made without subsequent reworking of the edges. A hammerstone was the most common percussive tool used during the Acheulean. The resulting artefact is usually easily recognizable given its size and irregular edges, as the removed flakes leave pronounced percussion bulbs and compression rings. A hammerstone produces a small number of flakes that are wide and deep leaving long edges on the tool