The invention relates to construction kit elements for use in children's building sets and in puzzles. A construction element according to a first variant comprises a flat rectangular base and a connecting unit. The connecting unit is comprised of four groups of projections. The projections of the first group are tubular and have an annular cross-section. The projections of the second group are tubular and have a square cross-section. The projections of the third group are in the form of rectangular plates with projecting shoulders. In the fourth group the projections are disposed in the corners of the base and are in the form of L-shaped members. A second variant of the construction kit element comprises three of the four groups of projections. The variants of the invention provide construction kit elements with enhanced functional capabilities.