Abstract: A self-tensioning printing cylinder lock for fitting longitudinally in grooves formed between printing saddles on diametrically opposite sides of a printing press cylinder. Such lock includes a longitudinally extending base plate having a longitudinally elongated tensioning bar disposed in overlying relationship with respect thereto. The opposite extremities of such bar are urged toward an extended position away from the saddle edge by a pair of identical springs to thus maintain such bar to a positioned aligned longitudinally with the printing cylinder as a result of such biased spring tension. Consequently, as the length of such printing plate mounted on the saddle varies during operation, the tensioning bar will draw the transversely opposite sides of such printing plate toward such extended position with uniform force to maintain the plate tensioned irrespective of variation in plate length.