Abstract: This invention relates to the alignment of the edge of an element in the form of a sheet or plate of small thickness for the purpose of edge-to-edge assembling of the same with others on a work bench. Each positioning member comprises a translatorily and rotatorily displaceable finger, and a member for control of its linear and angular positioning, the finger being arranged to assume an active position for which it is in contact with the edge of one element and a retracted position for which it allows of laying along-side the edge of a second element. The invention applies in particular to edge-to-edge alignment of steel plates which are plane or shell-shaped for the purpose of butt welding the same on a longitudinal bench.