Abstract: A running yarn is spliced into a running tow by entangling filaments of the tow with and about filaments of the yarn with an air-jet device, the leading portion of the yarn is severed to leave a small protruding tail, and the tail is entangled within the tow with a second air-jet device. The air-jet devices comprise two halves which are separated and positioned on each side of the tow until a splice is to be formed; they are then closed to form cylindrical treatment chambers of diameters which impart a rounded shape to the tow, so that filaments are entangled about the yarn by the air jets. The air-jet devices are preferably designed to provide a forwarding action on the filaments.