õmbluse juurele kinnitatud metallriba või varras, hoidmaks õhupilu püsivana ja sidumaks õmblust liiga suure õhupilu korral (vt juure pilu), a metal strip or bar prepared for a groove weld and inserted in the joint root to serve as a backing and to maintain the root opening during welding; it can also bridge an exceptionally wide root opening due to poor fit (see: root opening)