Perforated lockers are similar to the standard types of locker, but the door and walls are made largely or entirely of perforated steel, with hundreds of holes creating a strong mesh arranged in a diagonal pattern. This is used where good ventilation is required, or where, for security reasons, it is necessary that the contents can be examined visually while the doors are locked.
There is a luggage storage service a short one minute walk from Union Station in downtown Denver - LUGDEN. You can make a reservation online - lugden.com, call - (303) 747-5600, or show up as a walk-in. They offer hourly, day, overnight and weekly bag storage. Great place to store your luggage if you're on a layover from Denver International Airport, or going to a concert, or headed to a Rockies game at Coors field and want to enjoy yourself without having to lug your bags around.