An attachment device configured to be attached to opposed sides of an automotive creeper is disclosed herein. The attachment device includes: a first generally L-shaped member, a second generally L-shaped member, a connecting member slidably coupling the first generally L-shaped member to the second generally L-shaped member, and at one least pair of securement devices configured to respectively attach the first and second generally L-shaped members to the automotive creeper. In one or more embodiments, a width of the attachment device is selectively adjustable so as to accommodate a plurality of different automotive creepers having varying widths. An automotive creeper system and a mechanics chair using the attachment device are also disclosed herein.