The invention relates to a fastening block for mounting objects on a profiled rail (12) having an at least approximately rectangular cross-section. The fastening block comprises a housing part (14) with at least one claw (26), which is fixed to the housing and reaches over the profiled rail (12) so that the housing part (14) rests against two faces of the profiled rail (12) via contact surfaces that are parallel to the profiled rail (12). The fastening block also comprises an L-shaped moving clamping part (28) which, with its first L-limb (30), is mounted on the housing part (14) in a manner that permits it to pivot about a first axis (32) that is parallel to the contact surfaces and which is pretensioned into a clamping position in which it reaches around the profiled rail (12) with its second L-limb (34) provided in the form of a claw. Lastly, the fastening block comprises a tightening device (40, 46, 72) for tightening and blocking the clamping part (28) in the clamping position. A draw rod (40) is coupled to an actuating extension (36) of the first L-limb (30) of the clamping part (28) in a manner that enables it to pivot about a second axis (38) that is parallel to the first axis (32), said actuating extension being aligned radial to the first axis (32). The draw rod extends approximately parallel to the second L-limb (34). The tightening device has a tightening screw (72) that is coupled to the draw rod (40) while being resistant to tensile forces and is directly or indirectly supported on the housing part (14).