"Ch" is a combination of letters that represents a specific sound in words. It is commonly found at the beginning or middle of words and is pronounced like a softer version of the "k" and "sh" sounds. Full definition
Since its discovery in the early 1940s, the presence of CH + in interstellar space has been a mystery because it is extremely reactive and hence disappears more quickly than other molecules. (alma-telescope.jp)
Pour into the center of the smoker and spread out evenly to 1/4 in ch thick in the middle of the bottom pan. (fieryfoodscentral.com)
See also the similar point made by Lewis Mumford, The Transformation of Man [Harper & Brothers, 1956] Ch. (religion-online.org)