D-ring

A D-ring is an item of hardware, usually a tie-down metal ring shaped like the letter D used primarily as a lashing point. The term is found interchangeably spelled in different forms, such as: Dring, d-ring or Dee-ring.
A D-ring may be used at the end of a leather or fabric strap, or may be secured to a surface with a metal or fabric strap; though there are D-rings with a middle body designed to be welded to steel. Ideally, a D-ring swings freely after it has been secured. D-rings may vary in composition, geometry, weight, finish and load (rated) capacity.
Though there are differences, a weld-on pivoting link is commonly called a D-ring.
To minimize obstruction when the D-ring is not in use, recessed tie-down rings are designed that accommodate the D-ring so it is flush to the surface. There are some non-recessed designs that have an adhesive base. The corresponding work load limits (WLL) must not be exceeded.
Lashing points and disambiguation of the term.
Applications of D-rings include: