In accordance with the invention, there is provided a system and method for checking a mask layout including sub-resolution assist features (SRAFs). A checking program divides each edge of each main feature into sections, forms a set of segments by searching perpendicularly over a distance to determine if any portion of a feature is located within the distance. Segments are then flagged based on whether a feature located within proximity to that segment. A classification program may then classify each of the main features based on the segment data.