Abstract: An insulative frame-strip assembly comprises metallic inner and outer side members splined together by a rigidly-acting insulating or frost-barrier splicing strip. These three main parts are extrusions assembled by transverse movements, instead of being threaded end for end or requiring molding of the splicing strip in situ. Inadvertent disassembly in handling is prevented by locking made effective by a pressed-in locking strip. The locking may use interlocking formations or only friction, and either may be aided by torsional pressure. The locking strip is inserted through the pane-receiving channel so that inserting the pane therein prevents removal of the locking strip and adds to its locking forces. Hooked webs on the two metal side members extend transversely in slightly spaced parallel planes, the end of each being a flange extending toward the other web and snugly engaging the spline strip to use its compressive strength.