There are plenty of convenient places to store your luggage in Denver, from downtown to Lincoln street to Capitol Hill and Commons park. The cost is just US$6 per day, and check in time is just 3 minutes. So basically, in the same time it took to make that instant cup of Ramen before rushing to the airport, you can be in and out the door with no luggage to weigh you down.
Material: steel is the traditional material; but wood, plastic, or laminate are sometimes used. Plastic or laminate lockers are sometimes advocated in environments, such as near swimming pools, where moisture accumulation may cause steel lockers to rust over time. They can also be used in external applications where internal space is not available.
Dimensions (Note that, in English-speaking countries, even those commonly using metric measurements now, locker dimensions are usually clean numbers of inches or feet, while the corresponding metric measurements are uneven, involving decimal places when precision is required, presumably resulting from continued use of locker designs based on feet and inches, unchanged for decades other than for cosmetic features.):
Tiers: may be specified as single-tier (full height), two-tier, three-tier, etc., meaning that the lockers are stacked on top of each other in layers two high, three high, etc. Tiers are commonly up to eight high; on occasion, even more tiers may be found, in the case of very small lockers for such purposes as storing laptop computers. The most common numbers of tiers found in lockers are, in order, one, two, and four; three-tier lockers are rather less common, and other numbers such as five, six, or eight even less common still - seven almost non-existent. Since locker cabinets are most commonly 6 feet (182.9 cm.) high (although there are exceptions), the height of individual lockers varies according to how many tiers are accommodated within the cabinet. The height of individual lockers is usually approximately 6 feet (182.9 cm.) divided by the number of tiers, so that two-tier lockers are about 3 feet (91.4 cm.) high, three-tier lockers 2 feet (61 cm.) high, four-tier lockers 1.5 feet (45.7 cm.) high, and so on. Standard features often vary according to the number of tiers: single-tier lockers usually include a shelf about a foot (roughly 30 cm.) from the top, and a hanging rail (sometimes with one or two hooks) immediately underneath that, at the top of the large compartment beneath the shelf; two- or three-tier lockers usually lack the shelf, but include the hanging rail; lockers with four or more tiers usually have none of these fittings, but consist of just the bare compartment.