In considering the Pre-Chellean implements found at St. Acheul in 1906, we note(14) that at this dawning stage of human invention the flint workers were not deliberately designing the form of their implements but were dealing rather with the chance shapes of shattered blocks of flint, seeking with a few well-directed blows to produce a sharp point or a good cutting edge. This was the beginning of the art of 'retouch,' which was done by means of light blows with a second stone instead of the hammer-stone with which the rough flakes were first knocked off. The retouch served a double purpose: Its first and most important object was further to sharpen the point or edge of the tool. This was done by chipping off small flakes from the upper side, so as to give the flint a saw-like edge. Its second object was to protect the hand of the user by blunting any sharp edges or points which might prevent a firm grip of the implement. Often the smooth, rounded end of the flint nodule, with crust intact, is carefully preserved for this purpose (Fig. 61). It is this grasping of the primitive tool by the hand to which the terms 'coup de poing,' 'Faustkeil,' and 'hand-axe' refer. 'Hand-stone' is, perhaps, the most fitting designation in our language, but it appears best to retain the original French designation, coup de poing. [Illustration: FIG. 62. Primitive _grattoir_, or planing tool (side and edge views), of Pre-Chellean type, found in the lowest gravels of the terraces at St. Acheul. After Commont. One-quarter actual size.] As the shape of the flint is purely due to chance, these Pre-Chellean implements are interpreted by archæologists chiefly according to the manner of retouch they have received. Already they are adapted to quite a variety of purposes, both as weapons of the chase and for trimming and shaping wooden implements and dressing hides. Thus Obermaier observes that the concave, serrated edges characteristic of some of these implements may well have been used for scraping the bark from branches and smoothing them down into poles; that the rough coups de poing would be well adapted to dividing flesh and dressing hides; that the sharp-pointed fragments could be used as borers, and others that are clumsier and heavier as planes (see Fig. 62). The inventory of these ancestral Pre-Chellean forms of implements, used in industrial and domestic life, in the chase, and in war, is as follows: Grattoir, planing tool. Racloir, scraper. Perçoir, drill, borer. Couteau, knife. Percuteur, hammer-stone. Pierre de jet? throwing stone? Prototypes of coup de poing, hand-stone. It includes five, possibly six, chief types. The true coup de poing, a combination tool of Chellean times, is not yet developed in the Pre-Chellean, and the other implements, although similar in form, are more primitive. They are all in an experimental stage of development.