The present invention relates to a crane having a multiple-piece longitudinal structural part, in particular a tower or boom, whose pieces comprise corner arms or horizontal beams which can be placed next to one another and which can be releasably connected to one another by a mortise and tenon joint, wherein the mortise and tenon joint comprises a tongue which can be plugged into a tongue receiver and which can be fixed by means of at least one crossbar which can be inserted transversely to the plug-in direction of the tongue. In accordance with the invention, the crossbar of the mortise and tenon joint can be spread apart by a spreading device such that the pieces of the longitudinal structural part to be connected can be clamped to one another by spreading apart the crossbar.