 <unk> can be geometrically prepared in many different ways . The five basic types of weld joints are the butt joint , lap joint , corner joint , edge joint , and T @-@ joint ( a variant of this last is the cruciform joint ) . Other variations exist as well — for example , double @-@ V preparation joints are characterized by the two pieces of material each tapering to a single center point at one @-@ half their height . Single @-@ U and double @-@ U preparation joints are also fairly common — instead of having straight edges like the single @-@ V and double @-@ V preparation joints , they are curved , forming the shape of a U. Lap joints are also commonly more than two pieces thick — depending on the process used and the thickness of the material , many pieces can be welded together in a lap joint geometry . 
