Vertical bar holders can be either wall racks or floor stands. The floor stands are a metal box that sits on the floor with several holes in the top that the bars slot into. The weight of the boxes are sufficient to keep the bars stable and the design means your bars are kept together in easy reach.
Vertical wall racks are a great space saver, and enable you to store barbells at height, away from the floor. This utilises space that would otherwise be wasted. Each rack will typically hold three Olympic bars, that hang down below the rack.
Other options include wall racks that feature two separate brackets that need to be mounted the correct distance apart in order to hold the barbells safely between them. Due to how these look when filled, they are known as a barbell shelf.
It is also possible to combine bar and plate storage into a single rack, maximising space and minimising the amount of kit you need to buy.