have an original looking rubber floor mat in the 50 coupe i have i bought years ago when still available i think it is a little wider than the stock one so it overlaps the door sill i have been tucking it under the sill but if i go to check the master cylinder i have to take the sill out to roll back the mat to view MC question is should the mat be under the door sill or be trimmed along the door sill so dont have unscrew every time want to do something my thinking is a GM mechanic isnt going to take time to take sill off just to check MC

The mat goes up to the hump in the sill plate.

The Bel Air had carpet front and rear.

First Chevrolet to have carpet in front.

so then i am right on putting mat under the sill plate and the putting sill plate back on i did not want to cut or trim the mat i have made myself a resevoir using a motorcycle master cylinder have it mounted on the firewall then i ran a line to the floor MC blocking off any air passages so all i have to do is pop the hood and look at to see if needs fluid been on there for 5 yrs not leaking a drop thanks

THE MAT DOES NOT GO UNDER THE SILL PLATE.

A little off topic but... is there a part number and manufacturer name embossed anywhere on the mat?
Jeff

must have misunderstood the part of going up to the hump then i guess i will put the mat under the sill plate and loosely screw it down and the use a razor knife or scribe with something and carefully trim to butt up against the sill thanks again GENE you are always a great help PS/ the hubcaps are great cant wait till spring to put on car

JEFF the only marking that i can find only says CHEVROLET 1949-1954 i think i bought it from chevs of 40 many years ago when they were still being made same as with the trunk mat mine is the kinda tan color looks like original i think now they only have black

Yes, the mat with that marking is a reproduction. If your rear mat is original it was made by US Rubber or Baldwin, which from what I have been able to determine, was an alternate vendor. They were located north of Detroit and probably supplied the Flint assembly plant. Also embossed near the edge was a part number. The mat in my 51, which I am certain is original, is #4591535. My guess is that the US Rubber mat also had this part number. I asked for your help because I would like to know what the markings on an original front mat was.
And the rear carpet was NAILED to the floor.
Jeff

About how many nails and where? What kind of nails?

What I found on my 51 is a nail at each front corner of the carpet - one at he leading corner of the driver's side and one on the passenger side. They look like old style "cut" nails used for nailing into concrete. I found at least 1 brand new one under the front seat when I removed it last year. I will try to post a picture of the nail tomorrow or Monday.
Jeff

What were the nails driven into?

They were driven into the floor. I hope I am understanding your question properly. I have no idea if they were driven with a special tool (nail gun ?) or just an old fashioned hammer. I will get a photo later today or tomorrow.
Jeff

That's exactly what I was wondering. I've never heard of GM putting nails into steel to hold a mat, especially in the early '50's models. Anyone else run across this in an early BelAir?

The corners of the carpet in all models was nailed down to keep the CARPET in place and ALL Bel Airs have rear carpet.

Yes, as I said earlier, the rear carpet was nailed down at the corners, not the mat.
Jeff

I found nails in the floor of my 51 Bel Air when i cleaned the tar off the underneath.