Abstract: An apparatus and system for keeping the mortar between blocks uniform in thickness in both a vertical and horizontal direction makes use of a gage member having spacers for placement between the blocks and which are removable as soon as each block in turn has been placed in position with a mortar joint. Each separate gage member has for spacers a set of rods shorter than the thickness of the blocks for separating one block from the next when the mortar is placed between the blocks. A positioning guide on the gage member for engagement with an exposed side wall of the block determines how far the rods will project across the temporarily exposed face of the block. Adjacent the guide is a handle for placing and withdrawing the gage member as the laying of blocks progresses.