Here is what I use on my kayak trailer. One of them is a locking bin from Walmart I got for about 60 bucks, the other is not a locking one. I drilled two holes in the bottom fo the bin, ran a chain through one hole, the bottom mesh of the trailer and up through the other hole, and then connected the chains with a padlock inside the box so the box could not be lifted and taken when parked. The other bin is just held on with bungees and the lid is closed with a bungee cord as well. I use that for dirty fish bags, waders, and boots storage after I am done so that I don't have to put them in my car. I drilled a couple of holes in the bottom to secure it to the trailer with bungee and for drainage.