double U-butt weld, double U-groove weld, double-U-groove weld
põkkõmblus, kus liidetavate detailide servad moodustavad U-tähe kuju (vt põkkõmblus; vrd kaksik J-õmblus), a type of butt weld: a U-groove weld forming a U shape on the top and bottom when components are together (see: butt weld/groove weld; compare: double J-butt weld)
