If you've ever had a flat tire on a loaded trailer, you know it can be a challenge to jack it up and change the tire. This simple curved wedge "jack" or "chock" makes it very easy to change trailer tires and can be made in an hour from scrap wood. The design is based on the EZ Jack Wheel Chock. http://www.amazon.com/High-Country-Plastics-Wheel-Chock/dp/B000R5PMWE
Here's a video of how it works for a rear tire flat. If your front tire is flat, simply put the block behind the rear wheel and back-up. This block can also be used to chock a tire on any vehicle or trailer by turning it upside down and jamming it under a tire. Very handy.
The first thing to do is cut out a wooden template of the jack using the drawing below (pic 2). The squares in the drawing are 1" x 1". I created a grid of 1" squares on a piece of 1/4" plywood (pic 1) and cut it out on my bandsaw (pic 3). Alternatively you could make your template from cardboard, poster board, or even paper but I like to use wood so I can save them for future use.