There are eighteen meanings listed in OED's entry for the phrase custom, one among which can be labelled out of date. See ‘Which means & use’ for definitions, use, and quotation evidence. of tapping his fingers apply indicates an act or approach followed with regularity and typically via selection. https://tradeshowplanningadamexpo65429.blue-blogs.com/43511694/exhibition-stand-design-adam-expo-stand-for-dummies