To square the area for your new tunnel we will use the 3-4-5 method which is based on the mathematical formula called Pythagorean Theorem (a2 + b2= c2).  While this method uses 3ft-4ft-5ft as its reference you may also double or triple the numbers to get the same result.  For example, 3-4-5ft can also be 6-8-10ft or 12-16-20ft.  Please use this legend in the instructions for clarification:

LC1= "Top" left corner of your tunnel

RC1= "Top" Right corner of your tunnel

LC2= "Bottom" left corner of your tunnel

RC2= "Bottom" right corner of your tunnel

INSTRUCTIONS

1) Decide where the left corner (LC1) of your tunnel will be and drive one rebar into the ground.

2) Measure the width of your tunnel (14ft or 16ft) to the right of the left corner rebar (LC1) and drive a rebar. This is the "top" right corner rebar (RC1).

3) Measure the diagonal of your tunnel from the "top" left corner rebar (LC1) to the "bottom" right and drive a rebar using the following legend. This is the "bottom" right corner (RC2).  In order to find the correct diagonal angle measure the diagonal and "eyeball" a straight line from the "top" left corner (LC1) to the "bottom" left corner (LC2).  OR for a more precise measurement

             -14ft X 50ft= measure 52ft & drive a rebar. 

            -16ft X 50ft = measure 52.5ft & drive a rebar.

            -14ft X 100ft = measure 104' & drive a rebar.

            -16ft X 100ft = measure 105' & drive a rebar.

4) Repeat Step 3 measuring from the "top" right corner (RC1) to the "bottom" left corner (LC2).

5) String a tight line from the "top" left corner (LC1) to the "bottom" left corner (LC2) for a straight line to begin marking & placing rebar for the bow spacing (48" apart for 4ft bow spacing or 50" apart for 5ft bow spacing).