Based on the study of the thresholding method of the morphological rank order hit-miss transform (ROHMT), a one-channel rank order hit-miss transform is proposed and a rank order grayscale erosion is developed to implement the ROHMT and its extension. Compared with the conventional complement encoded hit-miss transform (HMT). Only the original image is used. Based on this implementing scheme, the HMT-based morphological processing systems can be greatly simplified; Its immunity to noise and processing capacity are both increased. A proof-of-principle experiment is conducted and the experimental result is given.