Select a hook rug backer six inches wider and longer than the shag area rug you want to make. The mesh backing is sturdy, net-like fabric woven into a grid of squares up to 1/4 inch in size. The mesh fabric has horizontal and vertical threads. Each square or opening has two horizontal bars and two vertical bars forming the square. A horizontal bar is a horizontal thread between two vertical threads. Buy a thick yarn in the color you want.
Cut a piece of notebook cardboard 3 inches by 6 inches. Fold the cardboard in half lengthwise so that you have a 1 1/2 inch by 6 inch folded cardboard. Place a pencil inside on the fold.
Wrap the yarn around the cardboard evenly. Don't stretch the yarn. When you reach the end of the cardboard, cut the yarn along the open end of the cardboard. This will give you yarn pieces all the same length. Keep your cardboard to make more pieces later.
Insert the hook end of the rug hooking tool under a horizontal bar of the mesh backing. Bring the hook up through the opening above the horizontal bar. As the hook emerges upward, the metal latch on the side of the hook will fall back, opening the hook. Start hooking the rug 3 inches from the top and side edges to allow for finishing.
Wrap a yarn piece around the latch hook tool near the handle. Make the ends of the yarn even. Bring the yarn over the horizontal bar of the mesh backing and place the yarn into the hook.
Pull the hook back toward you while you hold the yarn in your other hand. The latch will close as you pull back under the mesh. Let go of the yarn, and pull the hook through the mesh. The yarn will be tied in a knot over the horizontal mesh bar. Tug on the yarn to make it tight and move one space to the right and repeat. Continue until you reach 3 inches from the right side. Move down a row and continue until you reach the bottom of the rug. Allow 3 inches of empty mesh along the bottom edge.
Cut bias tape long enough to wrap around the rugs four sides and overlap 1 inch. Fold the mesh under so that you can place the bias tape over the fold and the edge of the tape will touch the yarn. Start in the middle of any side of the rug. Sew the bias tape to the rug. Fold your corners. Tuck the overlap fabric under 1/2 inch to create a clean edge. Sew past the end. Trim off the excess rug mesh on the back side of the rug.