A technique is described for fabricating simple metal structures with the scanning tunneling microscope (STM) which have dimensions of 10’s to 100’s of nanometers and are partially electrically isolated from their environment. The basic idea is to deposit a very thin metal film on an insulating substrate, and use the tip to machine gaps through the film where lateral electrical insulation is desired. A brief account is given of the technical issues involved in using the STM in this way. These include locating the metal-insulator interface, tip selection criteria, and variations in the tip’s machining properties. A 190 angstrom thick gold film deposited on mica is used to demonstrate the technique. Two potentially useful structures are shown which have been machined in this film : a wire segment 70 nm wide, and metal pads with widths of 240 nm and 50 nm.