An engagement unit for insertion on and engagement with a threaded bolt (33) is provided with an inner part (1) and with an outer part (2) that can be slid onto the inner part (1). The inner part (1) and the outer part (2) are configured with torque receiving means (8, 9, 23, 24) for transmitting a torque applied to the outer part (2) to the inner part (1). After the inner part (1) has been slid onto a threaded bolt (33) in a pre-assembly arrangement in which latching means configured on spring arms of the inner part (1) and cooperating with the threaded bolt (33) are able to slide along the threaded bolt (33), the engagement unit according to the invention can thus be inserted onto the threaded bolt (33) and, once the outer part (2) has been slid onto the inner part (1), can be tightened in the manner of a screw.