By providing a plurality of preformed components which are quickly and easily affixed in engagement with each other, a final construction is realized which peripherally surrounds any desired mattress configuration in cooperating association therewith. In this way, a new foam plastic product is achieved which is capable of being quickly and easily mounted to mattress constructions peripherally surrounding the mattress and providing an enhanced side support system. In this way, any desired mattress size or configuration is capable of being peripherally surrounded with a foam support assembly for enhancing the mattress construction and configuration. Furthermore, by employing the present invention, a rapid, convenient, and virtually labor free assembly is realized.