Chocks being parts of machines; trailer restraining systems comprised of a restraint arm, sensor and lock for use in conjunction with a wheel chock; trailer restraining systems comprised of a recessed locking hook for use in conjunction with a wheel chock; trailer restraining systems comprised of an electro-mechanical hook and control panel for use in conjunction with a wheel chock; trailer restraining systems comprised of a restraint arm and integral push bar for use in conjunction with a wh...