Measure and mark the 10-foot board to make two 33-inch sections and four 12-inch sections.
Saw off the 33-inch sections with a hand saw or miter saw, leaving a straight edge. Saw the 12-inch sections so there is a 45-degree angle on each end. Use a miter saw or a protractor and hand saw to ensure accurate angles.
Place the two 8-foot boards 33 inches apart on a flat surface. These are the trellis legs.
Place one of the 33-inch boards over the top of the trellis legs so the edges of the top board are flush with the outer edges of the 8-foot boards. Nail the 33-inch board to the top of the trellis legs using two nails on each side.
Place two of the 12-inch braces between the underside of the 33-inch board and the inside edges of the trellis legs so that the cut edges of the braces are flush with the edges of the other boards. Nail the braces in place, using two nails on each end.
Measure and mark 20 inches up from the bottom of each trellis leg. Lay the other 33-inch board between the legs at this marking and nail it in place.
Place the remaining two 12-inch braces between the top side of the 33-inch board and the inside edges of the trellis legs so that the cut edges of the braces are flush with the edges of the other boards. Nail the braces in place. The trellis frame is complete.
Measure and mark screw placements every 4 inches along the front side of the 33-inch and 8-foot boards. Install screws into each of these markings.
Tie one end of a piece of clothesline or wire around the bottom screw on either of the 8-foot boards.
Run the line horizontally across to the opposite screw, then up to the screw above, then horizontally to the opposite screw, then up to the screw above. Continue this pattern until you reach the top of the trellis. Tie a knot at the end and cut off excess line.
Tie one end of the clothesline or wire around the first screw on either side of the 33-inch board at the top of the trellis.
Run the line vertically down to the opposite screw, making a loop around each horizontal line you cross. When you reach the bottom screw, run the line to the screw next to it and work your way up to the opposite screw on the top. Continue this pattern until the trellis is complete, and tie a knot at the end.
Bury the trellis legs 20 inches deep in the ground so the 33-inch horizontal board is flush with the ground.