Bamboo Shanks 6 pairs Shoes Boots Making Leather Sole Repair Bamboo Shanks for Arch Support for Shoe Making This auction is for 6 pairs. Dimensions of a shank: Length: approx 5 inches, Width: 3/4 of an inch or 2 cm, Thickness: 2.5 mm. Shoe shank is a curved piece of material located above the outer sole at the narrowest or middle part of the shoe between the heel and the ball of the foot just below the arch. A shank is needed to help add extra support to the arch area of the shoe.