Place one 6-foot ladder on a flat surface running horizontally and position yourself at the top end of the ladder.
Place a 16-inch 2-by-4 section between the two sides of the ladder at the top end. The 2-by-4 should be placed so the depth of four inches matches the thickness of the ladder. Drive two 5-inch screws though each end to attach the 2-by-4 to the ladder securely.
Place the second 6-foot ladder at the top end of the previously placed ladder to create a span of 12 feet. Press top and bottom ends together to eliminate any gap.
Place one 2-inch wide door hinge on each of the two joining points. Drive two 3 1/2-inch screws through the end of each hinge to join the ladders together permanently.
Fold the top ladder over the bottom ladder to store. When using, place the hinge side closest to the building away from you so the ladders do not fold.