In cycling slang, on the rivet refers to putting out maximum effort, and derives from the way cyclists lean all the way forward on the hard bicycle seat, which traditionally has a flat rivet in the very front. This is part of a complete episode...
rivet n.— «An apprentice ironworker who does jobs such as running for coffee and getting tools for the journeymen. Rivet: Another nickname for an apprentice.Rivet: Another nickname for an apprentice.» —“Chicago Speak” by...