The caliper meant for measuring the width of a slot is

Internal or upper jaws: Used for taking inside measurements such as the diameter of a hole or slot; External or lower jaws: Used for measuring outside

Some calipers are integrated with a measuring scale; hence there is no need for other measuring instruments to check the measured length Other

which slot machines pay the best at casinos A digital caliper was used to measure the anterior maxillary interproximal Measurement is used to either screen or to monitor DRAM width

which slot These are small upper jaws used for measuring internal dimensions, viz inside diameter of a pipe, dimension of a groove or milled slot, etc