OPTIMUS # 3254-004 GLI # 4300431 THIS IS THE STANDARD FENCE POST USED ON THE GLI / CANTAR ABOVE GROUND PROTECT A POOL FENCING THIS IS A SQUARE RAIL, WHITE PLASTIC, WITH ROUNDED EDGES. LENGTH: 42" THICKNESS BOTH WAYS: 1-1/2" THIS HAS RECTANGULAR HOLES 3" x 15/16" WITH SLIGHTLY ROUNDED CORNERS. THESE ALLOW FOR ATTACHMENT OF THE FENCE RAILS AND ATTACHMENT TO THE BOTTOM SUPPORT THIS HAS 2 HOLES ON 2 OPPOSITE SIDES FOR ATTACHMENT TO THE FENCE RAILS ON BOTH SIDES ONE HOLE STARTS 1" FROM THE TOP, AND THE OTHER 22-9/16" FROM THE TOP. THERE IS 1 HOLE ON EACH OF THE OTHER TWO OPPOSITE SIDES. THESE ALLOW FOR ATTACHMENT OF THE RAIL TO THE BOTTOM SUPPORT THIS HOLES STARTS 1" FROM THE BOTTOM THE END RAIL POST, #3254-001, IS VERY SIMILAR. IT HAS THE SINGLE HOLE ON 2 SIDES NEAR THE BOTTOM FOR ATTACHMENT TO THE FENCE SUPPORT. IT ONLY HAS 2 HOLES ON ONE SIDE AND THE OPPOSITE SIDE FROM THIS HAS NO HOLES, SINCE THE RAILS DO NOT GO ALL THE WAY THROUGH THE END POST.