Working on finishing up my firewall for my 24 roadster and ordered some parts, made some parts and in comparing it to my 24 touring, what I remember when I took everything apart. I found both hex nuts and square nuts. Is there a rule of thumb as to where one uses one over the other. My touring was redone 40 years ago, this roadster has never been apart. I did have to cut some stuff apart. I have hex nuts holding the steering column in, square nuts are used on the bolts to the firewall brackets, and ????? Maybe Russ has some insite. It's possible that some were replaced over the years, but want to put it back right. J

Jerome,
Go to the MTFCI website at modelt.org, and you will find three photos of an original firewall on a 1924 Tudor. This car has never been disassembled, and will answer your questions. I'm sorry I didn't post the photos hare, but it is too difficult for me to resize the photos.
I hope this helps,
Russ Furstnow

No problem with that the answer thanks.

Square nuts are properly called "carriage nuts." As a general rule, they were used with carriage bolts.

http://www.modelt.org/mtfcivb/showthread.php/1442-1924-Firewall

When I restored my '25 pickup, I used the Ford Service book for reference. You can't go wrong with that! I also use the blackening solution from Eastwood to give the bolts the original raven finish look. There are no visible square nuts on a '25 firewall! There are lots of square nuts used on the body however, and they are all 1/2" across the flats, raven finished.

Russ one more question? Are all the nuts sized to have a 1/2" wrench fit on them? J

Firewall is in, and painted. If any one wants to know the two bolts in the corners are 5/16" and 2" long, I cut down 2 1/2" bolts to a fat 2 1/4" and I think 2" would have been fine. Still needing to place clips and wiring. Working on the hood shelf's today and picking up the lower steering bracket. Still need to assemble the front axle. Am hopping to have it all together for a ride on Labor day.

Jerome, Yes, all of the nuts are 1/2" hex. As you are aware, most are common 5/16" hex nuts with a 1/2" hex. The coil box bolts, being 1/4", use a "heavy hex" style nut, that has a 1/2" hex. The radiator support rod may be the only one that's different (if I am remembering right).

Here are the unrestored 24 firewall pictures that Russ spoke of. AS can be seen, the coil box nuts are hex, not square as on earlier years.

All the photos Royce supplied are correct. The special coil box nuts are 1/2 across, and are thin. They are the same ones that hold the front bow brackets to the front bow on tourings and roadsters. Additionally, the rivets that hold the felt to the firewall are the same ones that are used for the patent plate, and hood lacing. There are three on the '25s, and five on the '24s. Trivia I know, but some people like to know that stuff.