d-ring
nounUK /ˈdiː rɪŋ/
US /ˈdiː rɪŋ/
A D-ring is a metal ring shaped like the letter D that is used to hold or attach things.
She clipped her keys to the D-ring on her backpack.
OTHER MEANINGS
2. A piece of hardware on a horse's saddle or bridle used for attaching straps.
The rider fastened the bag to the saddle's D-ring.
3. A ring-shaped fitting on a dog harness or collar where a leash is clipped.
He hooked the leash onto the D-ring of the dog's harness.
4. A metal loop on a piece of luggage or equipment used for attaching a shoulder strap.
The camera bag has a D-ring on each side for the strap.