If you use jack stands to lift your boat from its trailer to do bottom work, such as painting or fiberglass repairs, you can use automotive jack stands -- with one important difference. Automotive jack stands, when used under a car, won't slide apart because the bottom of the car is flat. Automotive jack stands used under a boat can slide apart if the bottom of the boat isn't flat, and can lead to unpleasant consequences. The answer is to tie the jack stands together in pairs.
Items you will need
Jack stands (even number)
Dimensional 2-by-6 lumber
1/2-inch wood screws, 1 1/2 inches in length
Arc welding machine
Measure the width of your boat across the stern -- or beam -- with the measuring tape. Use the bolt cutter to cut a length of chain equal in length to half of the beam of your boat.
Measure a distance of 6 inches on the face of the 2-by-6. Mark the distance and use a carpenter's square and pencil to draw a line across the face of the 2-by-6. Use the circular saw to cut along the line. Repeat this process until you have one 6-inch-long piece of the 2-by-6 for each jack stand.
Drill two 1/2-inch holes upward through the part of the jack stand -- called the face -- that will come into contact with the boat.
Set one piece of 2-by-6 on the top of each jack stand and use your screwdriver to drive 1/2-inch wood screws through the holes in the face of the jack stand.
Use the arc welding machine to weld one end of the chain to the upright of one jack stand. Weld the other end of the chain to the upright of the other jack stand. Repeat this process for all other pairs of jack stands.