Fasten the D-ring wall mount to the wall using screws. Tie two 4-foot lengths of rope to the D-ring. Tie each length to the ends of one of the wooden dowels to form the end of the hammock. Cut the hemp cord into 40 pieces, 32 yards long each, with a sharp knife. Fold each piece of cord in half and loop it over the dowel. Bring the ends through the loops and pull tight.
Space cords evenly along the pole. Roll each length of dangling cord into a ball to prevent the cords getting tangled with one another. Do not secure the balls of cord, allow them to rest on the ground so they can unravel as needed. Take the first four doubled over lengths of cord in hand, so you have eight cords in total. Call the pairs of cords A, B, C and D for ease of reference.
Drape the leftmost D strand over the B and C strands. Drape the rightmost A strand over the leftmost D strand, under the B and C strands and back up over the rightmost D strand. Drape the leftmost A strand over the leftmost D strand, under the B and C strands, then up and over the rightmost D strand. Keep the B and C strands straight and pull the A and D strands tight to fasten the knot.
Slip the leftmost A strand under the B and C strands. Slip the leftmost D strand over the leftmost A strand, under the B and C strands, and back up over the rightmost A strand. Pull the A and D strands tight again to complete the modified square knot. Take the next eight cords in hand and repeat the process to create another square knot. Continue with the other eight sets of eight cords until you have an entire row of ten square knots.
Return to the first set of cords. Ignore the outermost two strands this time, so you have two A strands, two D strands, but only one B strand and one C strand. Repeat the process of tying the square knot. Repeat this square knot for the other nine cord sets, to complete the second row of the hammock.
Return to the first set of cords. Make a third square knot in this set, using all eight cords again this time. Repeat for the other nine sets. Continue to alternate between six- and eight-cord square knots on the cord sets until the length of the hammock is complete.
Tie each cord to the second wooden dowel using a double half-hitch knot. To do this, loop the cord around the dowel and pull tight, make a loop with the open end of the cord, around the dowel. Pass the open end of the cord through this loop and pull the cord tight. Repeat the process with the other cords until they are all fastened off.
Fasten the second D-ring wall mount to the opposite wall to the first. Tie the remaining two 8-inch lengths of rope to this D-ring using double half-hitch knots, for security. Tie the other ends to the second wooden dowel to complete the hammock.