Thinning on two-tone images is widely discussed. Two-tone images can be obtained by thresholding gray-level images. One major advantage of using two-tone images is that a binary image can be transformed into a continuous image to which many properties of topology can be applied. However, its tradeoff is that the thresholding function may lose some information of the original gray-level images. Rosenfeld introduced digital topology in early 1970's and fuzzy digital topology in late 1970's by the stimulation of Zadeh's fussy theory in 1965. It may be natural to process thinning directly on gray-level images. This paper proposes a template-based thinning algorithm on gray-level images and generates gray-level skeletons.