Canon TS-E 17mm f/4L TS-E17mm F4L Instruction Manual - Page 7

About the Shift Knob Cap Shifting will be easier if the supplied shift knob cap is mounted (p.4). However, for EOS cameras with built-in flash, the cap will come in contact with the camera during the lens' mounting/detaching, or during shift/rotation operation. The shift knob cap is recommended for use with EOS-1, EOS-1D, EOS-1Ds, and EOS 5D series. Mounting screw (Length 3mm) Shift knob cap Remove the shift knob screw. Mount the cap by squeezing it into the shift knob, and then fix it using the supplied screw. To remove the cap, remove the screw and pull out the cap. The screw (length 2.2mm) originally in the shift knob cannot be used to keep the shift knob cap in place. Always use the supplied screw. Use a watchmaker's screwdriver (Phillips head type) to remove or mount screws. ENG-6