Fender Seals - Why?

[cleszkie]

My Blazer never came with these, but I have a set of the metal brackets and bought new seals, but don't know If I really want to pull the fenders to install them.

What exactly is the purpose of the fender seals that mount between the side of the cowl and the front fenders? Some trucks got them, others didn't. Were they intended to reduce road/wind noise in the drivers compartment, improve sealing out of hot air from the engine compartment, or just an aesthetic improvement to clean up the door opening in that area?