What's the best method for securing bunks to a boat trailer. Tired of lag bolts backing out.

Thought about these stainless steel elevator bolts going in from top of bunk and securing bottom with locknut.

That oughta work. Last time I redid bunks I used galvanized lag bolts with silicone on the tip when screwing them in. But like you say sometimes they back out at the worst possible time!

use bit large enough to counter sink the head just past flush, keeps it from wearing on the carpet/hull.

they make a T nut type of head lock too, the square part fits and it locks in.

look in bulk fasteners, lowes/homey despot/ace etc.

Gracias Hop.

Use two nuts.