The first wheels I built were trued on a suspended frame. I put a pencil on top of the brake pads as a guide to make the wheel round, then I took off one pad and used it as a guide to dish and make the wheel flat. Knowing how to true a wheel on a frame comes in handy if you are on a tour, and need to true or repair or respoke a wheel. A number of years ago I did help another tourist rebuild her wheel using just the frame to true it.