Abstract: At current high cost of materials and labor, a preferred embodiment of the present invention makes possible easy do-it-yourself erecting of building block walls of proper alignment and of sturdy structure with easy handling materials of a simple nature, including an elongated sheet strip of corrugated cardboard having tar coating upper and lower broad faces of the strip, with length-wise spaced-apart markers indicating consecutive length units, and having on each of lateral side faces the corrugated cardboard series of consecutive openings, with the strip width being less than the width of the blocks under which and above which foundation and/or tiers of blocks are to be mounted such that a groove is formed for each additional tier between that tier and the support foundation or tier therebeneath, into such groove a mortar or other binder composition is insertable to be pressed into the corrugation openings in which the mortar or other binder hardens to set-up securing the mortar or binder against the possibi