A toy building element has sidewalls that include grooves and tongues by which the toy building element can be interconnected with a like building element. Each groove is formed between a pair of outwardly extending flexible ridges. In some embodiments, the tongue does not extend outward beyond the virtual plane of the sidewall that includes the tongue. In other embodiments in which the tongue extends outward beyond the tongue-sidewall virtual plane, the distance by which the tongue extends beyond the tongue-sidewall virtual plane is less than (a) the distance by which each ridge of the pair of ridges extends beyond the ridge-sidewall virtual plane, (b) the distance by each ridge of the pair of ridges extends outward to the ridge-sidewall virtual plane and/or (c) the distance by which each side of the tongue extends outward to the tongue-sidewall virtual plane.