An instrument for assembling an implant on a neck. The implant and neck being coupled via a taper having a taper axis. The instrument includes a frame having a distal portion and a proximal portion the distal portion of the frame including a retaining member adapted to engage a portion of the neck and a connector adapted to engage a corresponding feature of the stem. The instrument also includes a force applier retained in the proximal portion of the frame. The force applier includes a screw having a screw axis that is coaxial with the taper axis wherein the screw is adapted to engage the implant. As the screw is turned the force applier applies a force on the implant while the neck is held in place by the frame thereby causing the tapers of the implant and neck to engage.