An upper for an article of footwear, the upper comprising: a base layer (602, 802, 902, 1102, 1702, 1802, 1902) defining at least a portion of the upper; one or more polymer threads stitched to the base layer, the one or more polymer threads comprising a core comprising a first material and a coating comprising a second material, wherein the melting point of the first material is higher than the melting point of the second material, wherein the one or more polymer threads comprise: a first polymer thread set (610, 710, 760, 810, 910, 1110, 1820, 1920) stitched in a first pattern on an outer surface (604, 904, 1108, 1804, 1904) of the base layer, the first pattern comprising polymer thread lines oriented in a first direction, and a second polymer thread set (620, 720, 770, 820, 920, 1120, 1830, 1930) stitched in a second pattern on the outer surface of the base layer, the second pattern comprising polymer thread lines oriented in a second direction different from the first direction, wherein at least a portion of the first polymer thread set overlaps at least a portion of the second polymer thread set in an overlap area, and wherein at least a portion of the first polymer thread set is bonded to the base layer in the overlap area via the coating of the polymer thread in the first polymer thread set; characterized in that the upper further comprising a backing thread (940,1140) disposed on a second outer surface (606, 906) of the base layer opposite the outer surface, wherein the first polymer thread set is stitched around the backing thread to secure the first polymer thread set to the base layer. a base layer (602, 802, 902, 1102, 1702, 1802, 1902) defining at least a portion of the upper; one or more polymer threads stitched to the base layer, the one or more polymer threads comprising a core comprising a first material and a coating comprising a second material, wherein the melting point of the first material is higher than the melting point of the second material, wherein the one or more polymer threads comprise: a first polymer thread set (610, 710, 760, 810, 910, 1110, 1820, 1920) stitched in a first pattern on an outer surface (604, 904, 1108, 1804, 1904) of the base layer, the first pattern comprising polymer thread lines oriented in a first direction, and a second polymer thread set (620, 720, 770, 820, 920, 1120, 1830, 1930) stitched in a second pattern on the outer surface of the base layer, the second pattern comprising polymer thread lines oriented in a second direction different from the first direction, wherein at least a portion of the first polymer thread set overlaps at least a portion of the second polymer thread set in an overlap area, and wherein at least a portion of the first polymer thread set is bonded to the base layer in the overlap area via the coating of the polymer thread in the first polymer thread set; characterized in that the upper further comprising a backing thread (940,1140) disposed on a second outer surface (606, 906) of the base layer opposite the outer surface, wherein the first polymer thread set is stitched around the backing thread to secure the first polymer thread set to the base layer. a first polymer thread set (610, 710, 760, 810, 910, 1110, 1820, 1920) stitched in a first pattern on an outer surface (604, 904, 1108, 1804, 1904) of the base layer, the first pattern comprising polymer thread lines oriented in a first direction, and a second polymer thread set (620, 720, 770, 820, 920, 1120, 1830, 1930) stitched in a second pattern on the outer surface of the base layer, the second pattern comprising polymer thread lines oriented in a second direction different from the first direction, wherein at least a portion of the first polymer thread set overlaps at least a portion of the second polymer thread set in an overlap area, and wherein at least a portion of the first polymer thread set is bonded to the base layer in the overlap area via the coating of the polymer thread in the first polymer thread set; characterized in that the upper further comprising a backing thread (940,1140) disposed on a second outer surface (606, 906) of the base layer opposite the outer surface, wherein the first polymer thread set is stitched around the backing thread to secure the first polymer thread set to the base layer.