Aluminum plate 1/4 inch thick and 6'' diameter. To go under the deck to secure the mount base to the deck.

Sandwich the deck floor between the mount base and the under plate. 

Three 5/16 stainless steel bolts 2 inches long. With 5/16 stainless steel nylock nuts included.

Fits telescoping mount only.

Under Plate For Telescoping Monitor Mounts