Do these caps require any prep or painting before installation?

They arrive ready to install. If you want to match bed paint or apply a protective finish, sand lightly with 220-grit and apply automotive topcoat—but it's not required for function.

How do these attach to the bed rails?

They slide over factory rail edges and mount at OEM attachment points. No drilling. Hand tools and basic fastening hardware are sufficient for installation.

Will these fit if I've already added aftermarket bed accessories?

These are engineered for stock fleetside bed rails. Test-fit before committing to final fastening if tonneau covers or other rail-mounted gear is already installed.