a router bit for use with earth - moving equipment such as tractor scrapers , bucket loaders and dozers , composed of two parts , one affixed permanently to the apparatus and the other , which comprises the cutting edge , separable from the former for ease of replacement when worn and ineffective , thus obviating the need for expensive and laborious replacement of the whole router bit assembly . the upper and lower parts are joined by interlocking fingers and secured further by flex pins . the lower part , by means of a bar - like extension affixed to and positioned generally diagonally across the length of either side thereof , is prevented from lateral movement .