The invention relates to an apparatus for producing a weld seam on a foil bag with an ultrasonic hammer and an anvil, preferably with a weld side directed towards the ultrasonic hammer, the weld side having a long projection, so that the foil material of the foil bag can be clamped between the projection and the ultrasonic hammer. Preferably, the projection has at least one depression running parallel to the projection. The invention furthermore relates to an apparatus for producing weld seams on foil bags, wherein more than one of the above apparatuses are arranged next to one another and can be activated synchronously. The invention furthermore relates to a method for producing a weld seam on a foil bag, wherein the foil bag is clamped between an ultrasonic hammer and an anvil, wherein the anvil has a long projection on a weld side directed towards the ultrasonic hammer, and the foil bag is provided with a weld seam by means of an ultrasound, wherein the projection has at least one depression running parallel to the weld seam. The invention also relates to a foil bag with a weld seam, wherein the weld seam has at least two weld zones and at least three or four sealing wedges.