The invention relates to a tool for connecting cable cores, in particular of insulated telecommunication and data cables, to an insulation-piercing contact element, with a ram, which is formed with a ram head, by means of which the cable cores can be pressed into the insulation-piercing contact, the ram head being shaped in such a way that at least two cable cores can be pressed in simultaneously into at least two insulation-piercing contact elements lying next to each other.