Socket set is a tool used for tightening and loosening nuts and bolts. It consists of a handle and several interchangeable sockets that fit onto the handle. The most common type of socket set is the ratchet socket set, which uses a ratcheting mechanism to turn the socket. The term 'socket set' can also refer to a set of electrical sockets, such as those used to connect electrical appliances to a power source. In this case, the crossword solution 'eyes' refers to the holes in the sockets that allow them to be attached to the handle.