This boat trailer guide on pole is manufactured out of 1 1/2" square aluminum tubing with 1/8" wall thickness.  It measures 46" tall and has a 24.5" long leg for easy width adjustment to fit the sides of your boat as is goes onto your trailer.  It has an aluminum welded tab to serve as a stop for your pvc.  This guide pole is designed to have 2" pvc slide over top of it.  The pvc sleeves are available separately.  The guide poles typically attach via u-bolts to the main I-beam frame or into a cross member.