Strips
Take the finished width of the strip and add 1/2" for seam allowances. For example, 2" finished width + 1/2" for seam allowance = 2 1/2" width to cut. Place the plastic ruler on the fabric so that the cut edge of the fabric aligns with the markings on the ruler for the desired strip width. Always ensure you have a straight edge (on straight of grain) to begin with. Cut the strip. After several strips have been cut, it may be necessary to check and re-align the edge of the fabric. This is normal as a slight shifting of the fabric can occur during the cutting process.
Squares
Take the finished size of the square and add 1/2" for seam allowances. For example, 4" finished size + 1/2" for seam allowance = 4 1/2" width to cut. Cut a strip, the desired width. Place the strip on the cutting mat so that the longest edge of the strip is parallel to the lower edge of the mat. Trim the fabric selvedge off from the end of the strip making sure that this cut is perpendicular to long side of the strip. Now, place the ruler so that the marking for the desired square size aligns with the just trimmed edge. By now cutting along the edge of the ruler you will produce the desired sized square.
Half Square Triangles
Take the finished length of the straight side of the right triangle and add 7/8". This is the size of the square which, when cut in half diagonally, will produce two right triangles including seam allowances. For example, 3" finished straight edge + 7/8" = 3 7/8" size square to cut. Following the directions above, cut a square in the desired size. Next, take the ruler and carefully place it so that the straight edge runs from one corner of the square to the opposite corner of the square. Cut the square on the diagonal. This will result in two right angled triangles of the desired size.
Quarter Square Triangles
Take the finished edge of the straight side of the quarter triangle and add 1 1/4". This is the size of the square, which when cut in half twice on the diagonal, will produce four quarter triangles including seam allowances. Following the directions above, cut a square this size. Next, take the ruler and carefully place it so that the straight edge runs from one corner of the square to the opposite corner of the square. Cut the square on the diagonal. This will result in two right triangles. Do not move the fabric, Now, place the ruler to line up on the opposite corners of the square so that the straight edge runs through the center of the first diagonally cut line. Now cut on the edge of the ruler and you will produce four quarter square triangles to the required measurement.