Many bronze implements were reproductions, more or less modified, of neolithic models. Stone celts, knives, daggers, spear-heads, awls, chisels, gouges, sickles, and saws have their successors in bronze. Gradually, however, new forms were developed or invented. Bronze was of course at first reserved for weapons; and knives or knife-daggers probably preceded all others, because the metal was originally too scarce and expensive to be used for those which required a large expenditure of material.[554] Flat axes, resembling more or less closely the polished neolithic celts, were, however, manufactured early in the Bronze Age. After some time the sides of the narrow part of the celt, above the cutting edge, were hammered upwards,--probably in order to steady the blade against a lateral strain; and thus by insensible gradations the flat was transformed into the flanged celt; while a projection, commonly called a stop-ridge, was cast on the narrow part of the blade with the object of preventing it from being forced too far into its wooden haft. As the flanges became more marked, they were first confined to the upper part of the tool, and afterwards developed into wings which were hammered inwards so as to form a kind of rudimentary socket.[555] Celts of this form are called palstaves,--a word of Icelandic origin, which denotes a spade. In palstaves of another kind the part between the wings and above the stop-ridge was cast thinner than the rest, so that a groove appeared into which the haft could be securely fitted; and a loop was often added at one side to enable the attachment to be secured by bands of twine.[556] The final improvement was to cast the blade with a socket for the reception of the handle: but palstaves remained in use down to the very end of the Bronze Age;[557] while in some socketed celts the wings survive as mere ornaments upon the sides.[558] Like palstaves nearly all socketed celts are looped on one side, and a few on both.[559] Naturally the socket was not limited to celts, but applied also to knives,[560] chisels,[561] gouges,[562] and other tools. Socketed knives, however, are very rare in Scotland; and on the Continent, except in Northern France, they are almost unknown.[563] On the other hand the patterns of our socketed chisels and gouges appear to have been derived from some foreign source.[564]