A gripper head travelling through a shed in a weaving loom, has a longitudinal lateral guide surface (14A, 17A) along its gripper head body which is temporarily contacted by guide lever fingers in those positions of the head where its proper guidance is most critical, e.g. at the time of the weft transfer. The guide lever fingers are so driven by a drive mechanism that these fingers are withdrawn from the loom shed just as soon as the weft transfer is completed.