Bolting things down, also need to consider the size of the unit and what type of wood floor is on the trailer. A larger pressure washer or water tank can easily rip bolts out of the floor if the proper bolts/backing is not used. For some smaller tanks I have used e-track so I could removed stuff later easier and more quickly. I use lock washers, never really had an issue with these, and everything is a minimum 3/8, with bigger tanks having 1/2 inch bolts.