Why dont any flush mount rod holders come with backing plates

LEE'S SS BACKING PLATE FOR 30 DEGREE MEDIUM ROD HOLDERS

Lee's Tackle Lee's Stainless Steel Backing Plate F/30° Medium Rod Holders

Center Console Rod Holder Configuration for offshore fishing

Gemlux Backing Plate - Deluxe/Coastal

Trolling How-To: Setting Up A Pocket Sportfisherman - The Fisherman

Traxstech Aluminum Mounting Track

Fishing Rod Holders

Stainless Steel Backing Plate For Standard & Deluxe Rod Holders

Flat Top Rod Holders - Stores Rods Securely 90 degree rod holder for vertical fishing rod position The one-piece construction allows easy installation. Drain hole molded in bottom. Top measures 2 1/2 x 4 on the flange. Overall length is 9 1/2 with a 1 1/2 inside diameter. Install in 2 hole. All units have a molded in, rod index in bottom.

T-H Marine Rod Holder Flat Top Black [RH-2-DP]

30 Degree Flush Mount With Bar Bottom; Holds Single Spinning or Casting or Conventional Fishing Rod; Held By Rod Butt; Polished; Silver; 316L

C.E. SMITH C.E. Smith Flush Mount Rod Holder - 30 Degree / 53672A /

Lee'S Stainless Steel Backing Plate F/Heavy Rod Holders

Brooklyn 13.0 Pro Tandem Kayak for 2 or 3 People