Abstract: A yarn entangling device having a housing with an air pressure cushion in it for urging a piston normally outwardly of the housing. The piston has an air passage through it. Shifting the piston outwardly blocks the air passage. A blast nozzle is secured to the piston for being supplied with air through the piston. A baffle plate opposed to the blast nozzle defines a yarn channel. A holder supports the baffle plate for movement away from and into contact with the blast nozzle. With the holder moving the baffle plate toward the blast nozzle, the piston is shifted to open the air passage to the piston, and with the yarn channel opened with the baffle plate away from the blast nozzle, the piston is moved out of the housing by the air pressure cushion cutting off the air flow to the blast nozzle. A closing flap acts through a detent to secure the holder and baffle plate to close the yarn channel.