Lugs with a small hole drilled through them, allowing a spring bar to be pushed out from the side without needing to lever it out from the case, making strap changes faster and reducing the risk of scratches.
On a watch with drilled lugs, a small hole runs through each lug directly in line with the spring bar. A thin tool can be inserted through this hole to push the spring bar's pin inward from the side, releasing the strap without needing to lever the spring bar out from underneath, which is the standard method on watches without drilled lugs.
The practical benefit is speed and reduced risk of scratching the case or lugs during a strap change, since there's no need to pry against the case at all. Some brands omit drilled lugs deliberately for a cleaner, uninterrupted lug profile, treating the small visible holes as a design trade-off rather than a pure convenience.
They let a spring bar be pushed out from the side through a small hole, making strap changes faster and reducing the risk of scratching the case compared to levering the spring bar out from underneath.
Some prefer a cleaner, uninterrupted lug profile without visible holes, treating it as a deliberate design choice rather than an oversight.
They serve a similar convenience purpose but work differently, quick-release bars have a lever built into the bar itself, while drilled lugs rely on a hole in the lug to push a standard spring bar out from the side.