The invention relates to a device for allowing securing of a collision guard to a side of a vessel. A vertically oriented post is fixedly attached to and extends upwardly from the collision guard and has an upper part which is received in a gap formed between a pair of vertically spaced-apart horizontally extending retainer plates. An enclosure formed between the retainer plates surrounds the posts on those sides which do not face the hull of the vessel. Adjustable screw jacks extend through the openings formed in the enclosure side walls to selectively adjustably contact the side walls of the post to thereby secure the retainer plates to the post. An attachment bolster mounted on a top deck of the vessel allows fixed attachment of the retainer plates to the vessel.