Apparatus (20, 22) for mechanically joining advanced high strength steel (AHSS) comprising: a joining assembly for positioning adjacent a first sheet portion (28, 32) of advanced high strength steel that is contacted with a second metallic sheet portion (34, 30) at an interface of the sheet portions (28, 32), the joining assembly including a housing defining a light-safe chamber having an opening and also including an indexing member mounted on the housing with light-safe contact for movement parallel to the interface of the sheet portions (28, 32) between a heating position and a joining position, the indexing member including an opening positioned in the heating position adjacent the opening of the housing at a joining location of the first and second sheet portions, and the indexing member also including a die located (28, 32),in the joining position at the joining location of the sheet portions (28, 32); an actuator for moving the indexing member of the joining assembly parallel to the interface of the first and second sheet portions (28, 32) between its heating and joining positions; a laser assembly including a laser collimator for projecting a laser beam from within the housing chamber through the opening of the housing and the opening of the indexing member in its heating position to provide heating of the first sheet portion (28, 32) of advanced high strength steel at the joining location and after the heating the actuator moving the indexing member parallel to the interface of the first and second sheet portions (28, 32) to the joining position; a detector assembly for only permitting projecting of the laser assembly when the first sheet portion (28, 32) of advanced high strength steel is in light-safe contact with the indexing member in the heating position; a clinch punch or rivet ram for cooperating with the die in the joining position of the indexing member to mechanically join the heated first sheet portion (28, 32) and the second sheet portion (28, 32) to each other at the joining location; and a controller configured to operate the joining assembly, the actuator, the laser assembly, the detector assembly, and the clinch punch or the rivet ram for the joining operation of the sheet portions (28, 32). a joining assembly for positioning adjacent a first sheet portion (28, 32) of advanced high strength steel that is contacted with a second metallic sheet portion (34, 30) at an interface of the sheet portions (28, 32), the joining assembly including a housing defining a light-safe chamber having an opening and also including an indexing member mounted on the housing with light-safe contact for movement parallel to the interface of the sheet portions (28, 32) between a heating position and a joining position, the indexing member including an opening positioned in the heating position adjacent the opening of the housing at a joining location of the first and second sheet portions, and the indexing member also including a die located (28, 32),in the joining position at the joining location of the sheet portions (28, 32); an actuator for moving the indexing member of the joining assembly parallel to the interface of the first and second sheet portions (28, 32) between its heating and joining positions; a laser assembly including a laser collimator for projecting a laser beam from within the housing chamber through the opening of the housing and the opening of the indexing member in its heating position to provide heating of the first sheet portion (28, 32) of advanced high strength steel at the joining location and after the heating the actuator moving the indexing member parallel to the interface of the first and second sheet portions (28, 32) to the joining position; a detector assembly for only permitting projecting of the laser assembly when the first sheet portion (28, 32) of advanced high strength steel is in light-safe contact with the indexing member in the heating position; a clinch punch or rivet ram for cooperating with the die in the joining position of the indexing member to mechanically join the heated first sheet portion (28, 32) and the second sheet portion (28, 32) to each other at the joining location; and a controller configured to operate the joining assembly, the actuator, the laser assembly, the detector assembly, and the clinch punch or the rivet ram for the joining operation of the sheet portions (28, 32).