Abstract: A retention and deployment mechanism for pivotable guide fins on bombs or missiles includes a cup shaped yoke slidably mounted on a shaft. The device is mounted in a central region of the bomb tail and engages tabs on each of the fins. The tabs are held between a retaining flange and pusher arms extending radially from the yoke. The retaining flange prevents pivoting of the fins until desired. A drive spring causes the yoke to slide axially, and the pusher arms push on the fins to cause pivoting to the deployed position. The yoke includes a head end with a cone shaped recess. Four balls seated in holes in the shaft contact the cone shaped recess to prevent movement of the yoke. A pin disposed in a bore in the shaft hold the balls in the seats. The pin includes a groove, and is movable by a spring to a position where the balls fall into the groove, thus releasing the yoke. A lanyard is attached to the aircraft and extends through aligned holes in the shaft and pin to retain the pin in position.