Apply a paint designed for texturing with a heavy roller. Cover to the wall. Start in the corners and smaller areas and continue to work on the larger areas.
Wrap a thin cord around the length of a clean three-inch roller cover and secure it by tying knots at the end. Trim the ends of the knots as short as possible. The cord will create the long, deep grooves seen in natural bark.
Roll the cord up and down on the surface until you get the pattern that you desire. The cord will leave its imprint as you are rolling. The knots at the end will give the impression of the knots found in natural bark. If you want larger knots, use the end of a cardboard roll and press into the wet paint. Vary the sizes of the cardboard rolls to create different-sized knots.
Wrap a thick cord around a larger roller cover and using the techniques in step 4 continue to create a bark wall texture on the larger areas of the door or wall.
Allow the paint to dry as recommended by the manufacturer.