A retainer for immobilizing a bucket containing a liquid material, such as paint or other relatively viscous liquids, during mixing the material or to prevent accidental tipping of the bucket, is formed with a ring-like socket within which the bucket is positioned. Laterally-extending wings are formed on the socket. The user stands upon the wings to hold the socket against the ground-supporting surface upon which the socket is supported so as to prevent rotational or other movement of the socket and, consequently, movement of the bucket. The socket is formed of a generally cylindrically-shaped, vertically-axised wall which is tapered inwardly from its upper edge to its lower edge at a sufficient slope to radially inwardly frictionally grip and temporarily lock the bucket within the socket. The outwardly extending wings are of sufficient size for supporting the user's feet on opposite sides of the socket so as to position the user generally above the bucket and enable the user to manually position and hold a mixing device in the bucket while the user's feet clamp the retainer, and consequently, the bucket, against the support surface.