The Dock Sides Slotted and Flanged Receivers with Cross Beam facilitate mounting on a 4' wide dock. Docks that measure 5' or 6' wide require our Cross Beam 30 inch Extension. The cross beam extension measures 30" and secures to the cross-beam member included with the slotted and flanged receivers. The extension sleeves into the Cross Beam and secures with stainless fasteners. The opposite end of the extension secures the rear backplate with stainless fasteners. There are multiple locations pre-drilled into the extension that will accommodate most standard dock widths.