You need to give a few more details about what you’re trying to do.
On a modern (1990s or newer) bike, drop-bar brake levers, whether brake-only, or an integrated brake/shifter’STI’ unit, have a rubber cover/grip over the base/mounting hardware. This rubber cover is the Hood; it comes as a part of the lever assembly, and is usually specific to a particular make or model lever.

Being that it’s a rubber grip surface, the hoods are subject to wear and damage, so you can often buy replacement hoods to repair or refurbish lever assemblies without having to replace the entire mechanism.