Slide carpenter's square (1) and move string (2) on line X-X until
B and C
string is flush with edge of carpenter's square. String will be at
right angle (90°) to wall (3).
Using chalk, mark point D of line X-X where string (2) is flush
Soldier C 2.
with edge of carpenter's square.
Do steps 1 and 2 again for line A-A and point E.
Using chalk, draw line C-C through points D and E.
GO TO FRAME 6