 The curb chain is usually a flat-linked chain, though it may be made of anything from a relatively mild flat leather strap to very severe designs with heavy chain or even solid metal bars.The noseband and curb chain are connected by a metal link that also includes the long shank that applies pressure to the nose, chin groove and poll when the reins are tightened.Although sometimes called a bitless bridle, technically, a mechanical hackamore is not a bridle, as a true bridle contains a bit.