Screw joints for wood products and constructions has not individual standard for dimensioning. Experimental observation of strength of preloaded screw joints of wood parts show, that screws to wood are more suitable for transfer of higher forces at drawing than nails, but their assembling must be realised according to construction standards, they must not be hammered and they must be screwed to pre-drilled holes (besides of self-cut wood screws). The assembling must be realised by controlled tightening moment for ensuring of dimensioned pre-loading. At joints with long-term loading there is necessary to renew the pre-loading by occasional screwing of the joint.