the invention provides a method of and a device for reducing pucker between layers of sheet material during a sewing process wherein an upper layer and a lower layer of material are fed to a stitch formation zone by means of a reciprocating lower feed - dog which engages the lower layer of the material and a first presser foot which overlies the feed - dog and urges the layers of material towards the feed - dog ; comprises the steps of tensioning the lower layer of material relative to the upper layer of material in the zone which precedes the stitch formation zone .