FIELD: construction. ^ SUBSTANCE: invention concerns construction specifically foundation engineering. Screw hole is made of one strip bended in straight lines set at an angle to the strip edges to form similar parallelograms alternatively located on the strip and oppositely directed. The strip is rolled into cylindrical coils joined together at the edges to form the outer and inner surface of triangular helical lines and helical surfaces. ^ EFFECT: simplified manufacturing process and enhanced technology. ^ 6 dwg
