as their highly concave form yields curving edges. The cross-section is irregular, often sub-rhombic, while the intersection between the faces forms an acute angle of between 60° and 90° degrees. The shape is similar to that of the core as the irregularities formed during knapping are not removed. The notches obtained were exploited in the production sequence. It is common that this type of manufacture yields "partial bifaces" (an incomplete working that leaves many areas covered with cortex), "unifaces" (tools that have only been worked on one face), "bifaces in the Abbevillian style" and "nucleiform bifaces". This type of manufacturing style is generally an indication of the age when a tool was made and with other archaeological data can provide a context that allows its age to be estimated. Hard hammer faces and edges These hand axes have a more balanced appearance as the modification consists of a second (or third) series of blows to make the piece more uniform and provide a better finish. The modification is often called retouching and is sometimes carried out using invasive retouching or using softer, marginal, shallow blows that are only applied to the most marked irregularities leaving scale-like marks. The modification of edges with a hard hammer was carried out from the beginning of the Acheulean and persisted into the Musterian. It is therefore not useful as an indicator of chronology (in order for it to be considered as a marker it has to be accompanied by other complementary and independent archaeological data). The hand axes arising from this methodology have a more classical profile with either a more symmetrical almond or oval shape and with a lower proportion of the cortex of the original core. It is not always the case that the retouching had the objective of reducing an edge's irregularities or deformities. In fact, it has been shown that in some cases the retouching was carried out to sharpen an edge that had been blunted by use or a point that had deteriorated. Soft hammer finish Some hand axes were formed with a hard hammer and finished with a soft hammer. Blows that result in deep conchoidal fractures (the first phase of manufacture) can be distinguished from features resulting from sharpening with a soft hammer. The latter leaves shallower, more distended, broader scars, sometimes with small, multiple shock waves. However, marks left by a small, hard hammer can leave