In April 1915 Second Lieutenant Roland Gerard Garvin of the British Army enrolled in a course of instruction at Staff College in Camberley, Surrey, England. There he attended lectures on tactical instruction, topography, field engineering, administration, organization, military law, and hygiene. One of his lecturers was Major Hubert Conway Rees, who had commanded a battalion during the retreat from Mons in 1914. These notes and drawings by Garvin are from a tour of field works that he made as part of the course and that was led by Major Rees. The notes indicate that Garvin learned how to create a loophole in a nine-inch (22.86-centimeter) and in a 14-inch (35.56-centimeter) wall, how to conceal an abattis or field fortification, and the measurements for an effective overhead cover. Major Rees stressed the need to use this knowledge along with common sense, as “trenching” was not an exact science. The DSO after Rees’s name is an abbreviation for Distinguished Service Order, a British military honor.