Complex sentence: The simplest method of checking a low grade square for accuracy is to draw a line across a board with a flat face and straight edge, then flip the square over 180 degrees and see if the blade aligns with the line just drawn.
Split into simpler sentences: The simplest method of checking a low grade square for accuracy is to draw a line across a board with a flat face and straight edge. Then flip the square over 180 degrees and check if the blade aligns with the line just drawn.