Measure the length and the width of your camper floor, using a tape measure. If you desire, you may draw a simple diagram of your camper floor on a piece of paper, writing down the measurements for each of the sides.
Purchase your rolls of carpet-padding foam, tacky on both sides, and your selected roll of carpet. When purchasing, try to ensure the rolls are at least as wide and as long as the camper floor area you are planning to cover, making your job much simpler.
Unroll your carpet padding outside of the camper on a flat surface and, using a yard stick and carpet knife, carefully cut out your floor pattern from the padding. Use caution to ensure your lines are precise and straight.
Unroll your carpet outside of the camper on a flat surface, but with the carpet area facing down. You will want the backing of the carpet facing up. Use your yard stick and ruler to cut out your floor pattern from the carpet roll, just as you did with the foam padding in Step 3.
Roll up the foam padding pattern you cut out, rolling it into a tight roll, and lay it in the middle of your camper floor. Unroll the padding while fitting it to the edges of the floor. Once you have unrolled the foam, walk on its edges to help it in making a non-slip adhesion to the floor.
Roll up the carpet pattern you cut out and roll it into a tight roll just as you did with the padding. Lay it in the middle of your camper floor and unroll while fitting it to the edges of the padding you laid down previously. Walk along the camper floor edges once again to seat the carpet down onto the padding well.
