tongue style sewn not just to the vamp, but also all or partway up the insides of the quarters, under the {{facings}, often perforated by the eyelets and any lace hooks
Bellows tongues can prevent water from seeping into a shoe past the lacing and provide additional padding over the insteps.
As with slip-on shoes, a bellows tongue must open wide enough to allow the foot to pass in and out of the shoe.
Material
Bellows tongues are often cut from the belly or other thinner, more flexible, and less desirable parts of the same hide as the upper leather, or from a complete different material.