It is an amazing instrument that was devised by Nikomides in order to carve the conchoid curve and with its help to solve two of the three eminent problems of antiquity, the doubling of the cube and the trichotomy (trisection) of the angle. It consisted of two stable vertical bars in the form of “T” and a moving one. The mobile bar was bearing a sliding pin inside the slot of the first vertical bar and a sliding slot around a pin (pole) of the other vertical bar.