Plastic mold key sheets are ideal for molds using the shim technique. Pour in extra mold material to create keys that may be embedded in rubber later. May be used to around the flange on brush-on molds (see example) to aid in registration. Key sheets work with silicone and urethane rubber products. A light spray of release (2500 or Eject-it 33 for silicone, 2300 for polyurethane) may be necessary to aid in the release of some rubber products.