Oilcloth, which today is made of plastic-covered material, was originally a woven fabric treated with linseed oil. The linseed oil made the fabric waterproof, and it was often used for tablecloths or picnic blankets as well as tent and tarp material. Like the modern vinyl and PVC versions, this style of oilcloth is stiff, making it suitable for outdoor use. You can make your own oilcloth tarp to suit your purposes, such as covering a truck bed or protecting other materials.
Put your pre-cut canvas fabric into the washing machine. This will allow you to account for any shrinking. Run the fabric through the dryer to dry it, or hang it outdoors in the sun.
Cut your fabric to the size that you would like your tarp to be, plus 1 inch all around.
Punch or cut grommet holes all around the edges of the fabric, 1 inch in from the edges. Use an awl if necessary.
Push the grommet side of a large grommet through 1 of the holes. Place the grommet onto the die part of the grommet punch, then place the washer side of the grommet on top of that.
Place the punch shaft through the middle of the grommet and rap it firmly with a mallet, until the edges of the grommet fold up around the fabric.
Repeat this process on the other grommet holes.
Lay the tarp to a wooden frame, so that the fabric is stretched taut.
Staple the fabric to the wooden frame, using a staple gun.
Paint a liberal amount of linseed oil over the entire surface of the tarp, until the fabric is soaked through.
Hang the wooden frame outdoors, and let the surface of the tarp dry for several days.
Turn the tarp over and paint linseed oil over the opposite side of the tarp, like you did in Step 4. Let the surface dry again for several days.
Cut the oilcloth tarp off the frame. Paint the cut edges of the fabric with linseed oil, then let them dry.