Abstract: A rotary lock seal includes a pin with an elongated shaft and an enlarged head at a rearward end. The forward end of the shaft has a peg projecting coaxially therefrom. An end cap has an enlarged head at a forward end and a central bore extending forwardly through the rearward end, forming an annular sidewall. An annular groove on the inner surface of the cap sidewall corresponds with a groove formed on the peg to retain a locking ring within the pair of aligned grooves when the cap is positioned over the peg on the pin. The locking ring prevents removal of the cap once secured on the pin.