The straining screw which needs to be slackened is accessible via the holein the housing at the front of the machine, directly above the blade. It'sa simple slotted screw, but you'll need a screwdriver with a 6" blade (thisis supplied with the jigsaw). Slacken 3-4 turns, then loosen the twobaseplate screws until the roller guide can be moved. Turn the blade 90degrees and pull. Insert a new blade at 90 degrees to the cuttingdirection, rotate the blade to the cutting direction and pull lightly tolock. Tighten the straining screw, then slightly press the roller guide tothe back of the blade and tighten the base plate screws. This informationis based on my Bosch PST 53A, which hopefully is similar.