Abstract: A plastic back-up shear plate is laterally disposed with a spring fit into the outwardly facing mouth of a metal window frame. The outwardly facing mouth is formed and defined by the window frame. The window frame is an elongated hollow body with opposing outer wall elements which define the outwardly facing mouth. The shear plate is snap fit into the mouth. The shear plate has laterally disposed opposite outer edge portions which are interlockable on the outer wall elements which define the mouth of the window frame. The shear plate has a lateral dimension slightly larger than the lateral mouth dimension which causes the shear plate to snap fit into the mouth with the spring fit. In one embodiment, the shear plate includes support ribs. In another embodiment, the outer base face of the shear plate includes at least one, and preferably two, shim elements which rise above the outer face. The shim elements may be arcuate elements. In another embodiment, compressible shim fingers are utilized.

Abstract: The plastic back-up shear plate is laterally disposed with a spring fit into the outwardly facing mouth of a metal window frame. The mouth is defined by the window frame. The shear plate has laterally disposed opposite outer edge portions which are interlockable on corresponding outer wall elements of hollow body metal window frame. In a perpendicular direction, the back-up shear plate has opposing edge portions which interlock on window frame mouths having a slightly different dimension. The shear plate is constructed and arranged to fit, with appropriate change in orientation, window frames of two different mouth openings. Multiple window frame mouths, on different window frames, are accommodated by a multiple sided back-up plate.

Abstract: The sizable plastic back-up shear plate is laterally disposed with generally a spring fit into the outwardly facing mouth of a metal window frame. For windows having smaller mouths, the shear plate is cut along a discardable edge portion. The outwardly facing mouth is formed and defined by the window frame elongated hollow body and particularly by outer wall elements which face each other in an opposing manner. The plastic back-up shear plate has laterally disposed opposite outer edge portions which are interlockable on corresponding outer wall elements of hollow body metal window frame which wall elements define the mouth of the window frame. An intermediately disposed locking lip is utilized on smaller frame mouth after cutting or separating off the bread away edge portion. The plastic back-up shear plate has a lateral dimension slightly larger than the lateral mouth dimension and thereby achieves a spring fit.