This is what the holder looks like mounted on the trailer. Because of the limited space between the boxes, I had to design the carrier so the fuel can could slide horizontally, for removal. The chock block actually holds the fuel can in place.

The carrier with the chock block removed. It is easy to see that the can, can now be easily slid out for removal. Security is provided via an inexpensive bicycle chain and lock, it's more of a psychological barrier than anything else.

This is what I started with, an ammo can which cost me little at the local surplus store. Caution, not all ammo cans are the same size. I found there to be 1/4 of an inch difference in width between boxes. The difference seemed to be related to the type of ammunition that the box was designed for.

Here are the tools and materials I used to make the carrier.

1. Electric hand drill with assorted bits.
2. Jig/saber saw with fine tooth metal blade.
3. Pop Rivet gun and pop rivets.
4. Straight edge
5. Pencil
6. File (for smoothing edges).
7. Sandpaper
8. Safety glasses
9. Tape Measure
10. Paint - primer and finish.
11. Lacquer thinner (cleaning prior to painting).
12. Tin snips (not pictured).
13. Vice grips (not pictured)

1. Remove the lid and set it aside, you won't need it. It comes off easily.
   
   
2. Drill out the spot welds on each end of the box, the ones that hold the hinge and the latch onto the box. While doing it like this looks difficult, it was the best way to apply enough pressure to get the drilling done. I used a 3/16 " drill. You might have to use a larger drill if the welds are too strong.
   
   Note: On the second box I did, the hinge was actually hardened a bit, I went through several drill bits in order to get the hinge side drilled. This was not the case with the first carrier I did.
   
   
3. Use a cold chisel and ball peen hammer to separate the spot welds and remove the hinge and latch parts.

4. Before this step, take a moment to think.

Perhaps in your application, the fuel container can be removed vertically from the top. In this case, you can rivet the chock block straps higher on the box than what I did. Perhaps flush at the bottom, they would actually be stronger. I had to fasten mine at the bottom like I did so I would be able to slide the container out sideways. If you want the sideways option, Scribe a line 2" down from the top edge Of the box all four sides. Otherwise, locate the straps higher up.

5. On the line you drew, drill a series of small holes just as wide than the jig saw blade so you have a place to start. Then use the jig saw to cut the box along the line you scribed. The more careful you are to get a nice even cut, the less smoothing you will have to do with the file. The blade tends to grab the metal as you go so be careful and go slow. Clamping some plywood on the inside might help the grabbing. This is also a very noisy procedure, protect your hearing if you are interested in being able to hear when you are older.

6. Now cut the piece you just cut off of the box in the middle, with tin snips.

7. Now you have two straps to hold your chock blocks.

8. Measure and mark a line 1" from the bottom edge along both sides. If you are not needing a sideways removal of the can, this step is not necessary.

9. Before doing this step, do a trial fit with your chock block and make sure that the bulk of the block is below the straps top. If you end up with the chocks being "top-heavy", the chocks could fly out when you hit those big bumps or during large wind gusts. Measure and draw a line 3 and 1/4 inches from the closed end as shown, on both ends. The masking tape is being used only to help clarify the process.

10. This photo shows the relation between the lines you made on the box and on the chock bracket.

11. Drill for one of the pop rivets. Watch out, the pieces want to sneak a little out of alignment as you drill. Remember to de-burr the inside of the box so the rivet will seat properly. Once one rivet is in, it is easier to make the final alignment. Drill the other rivet hole and install the second rivet making sure to keep things as visually square as possible. Perform the same procedure to the other side.

12. Using tin snips, cut an angle as shown to remove the sharp 90 degree edge on both sides.

13. This photo shows the relationship between the box and the chock block strap.

14. If you want to be able to slide the fuel can out the side, cut off the end of the box to match the outside edge of the fuel can, otherwise, bypass this step.

15. Attach the strap just the same as you did on the other end of the box. Notice that I used vice grips to hold the pieces securely while drilling and riveting.

16. Trim the corners like you did on the other end.

17. Here is what you got if things are done right. Note: I rounded top right edge corner. Things left to do, drilling mounting holes in the bottom, removing all the sharp edges, sanding, priming and painting. If you opted to leave both ends intact, you should probably install some drain holes for rain water which might accumulate.

18. When mounting the unit on your trailer, be certain that you have no exposed bolt heads that will wear a hole into the bottom of the container. I used elevator bolts and lock nuts.

19. This is what is left of the original ammo can.