Cut fabric strips according to tool. Example: for a 3" finished triangle, cut 3 1/2" strips. Layer up to 4 strips of fabric and place triangle to far end with tool aligned so desired triangle height is even with bottom of fabric strip. Bottom of black triangle at top of tool should be even with top of strip.
Trim away corner on left side of fabric strip. Cut up right edge of tool. Flip tool and align again. Make cut up right side of tool.
Continue in same manner to end of strip. Use chart for suggested sizes and number of triangles to cut.