This seller on EBAY has really well made attachment devices for attaching Beam Antennas to Masts. Check out his other items for antennas too. http://www.ebay.com/itm/Aluminum-Antenna-Plates-2-Mast-to-2-Boom-/251823062381?pt=US_Radio_Comm_Antennas&hash=item3aa1d2fd6d Gary J N5BAA