An apparatus and method for rigidly joining construction elements to one another based on providing construction elements each having a connecting bore formed therethrough, positioning elements each having a connecting bore formed therethrough for aligning the connecting bores of adjacent construction elements, and partially expandable locking means dimensioned to extend through the aligned connecting bores of at least two construction elements and one positioning element. The construction elements and positioning elements are further equipped with engagement grooves and engagement ribs, respectively, for positioning adjacent construction elements in any number of predetermined angles. The locking mechanism has a radially expanding portion capable of locking the previously positioned construction elements in a rigid fashion.