Thanks to Wali for his excerpt from the Idiot’s Guide.

How? Poke large hole(s) in your perfectly good Kayak and set it in place with some stick-um and screws. Seriously though, it really is about that simple. A 2 1/4″ hole saw works real well to poke the hole and I like 3m 4200 as a sealant. Don’t drill the screw holes until you put the holder in place and rotate it to the position you want your rod to point in and it fits inside your hull (I shortened mine some). Be careful and don’t over tighten the screws (just enough to pull it almost flush and make the sealant ooze (wipe clean) Make sure you use stainless steel hardware. Most come without a bottom and you need to cap it. I sanded mine down some and fit an abs cap (2″ I think) on it and sealed it   I have three. Hope that helps