So-called 'body-builders'' clamps (i.e. medium-heavy-duty C-clamps, as
made by Armstrong, Williams, Billings & doubtless others): what sort
of body-building is involved? Automotive carriage work? (Maybe from
the days when auto chasses were made partly of wood?)

I would think automotive, or other transportation (trains, for instance), yes.

Sheet metal started to become used for skinning carriage in the 1890's, then automobiles from 1900. Wood doesn't leave autos til the late 1930's. So you have a 30-40 years they would have been popular.

On the other hand, the Armstrong listing "for body-builders,
wood-workers, and allied trades" is from an industrial supply
catalog from 1955, though probably retaining the language of
earlier editions. Not sure how old the Williams "body-builders'"
clamp no. 402 is.

I can remember a 52 REO truck with a wood framed steel skinned body.  Brockway & Mack both had wood framed cabs in the 50s, as well as removable wood floorboards on conventional models.

Quote from: Aunt Phil on March 14, 2016, 01:05:15 PM
I can remember a 52 REO truck with a wood framed steel skinned body.  Brockway & Mack both had wood framed cabs in the 50s, as well as removable wood floorboards on conventional models.

And some of the English firms were hand-making trucks with wood frames into the 50s.  For that matter, the MG-TD had a lot of wood.

Don't forget the Morgan!

Quote from: Papaw on March 14, 2016, 11:35:12 PM
Don't forget the Morgan!

Ahhh, the beloved 3 wheeled boattail and the 4 wheeled version that looked so like the MG-TD.
MG-A has plywood floorboards, I can lay hands on one 6 miles from me.

Steel truck bodies continued with oak framed steel pannels into the 60s because it was a stronger combination, and there really wasn't a good fastening system for sheet steel to structural. 

In minor ways, European makers continued to use wood, mainly plywood, into the 70s and later.  Three examples come to mind:

1.  We had a Volvo station wagon, 1973 year, that used plywood for the panels that covered the storage well in the back (and that could be replaced by similar panels, with upholstery on them, to make a back seat).

2.  My son briefly (thank goodness) owned a Triumph Spitfire* on which the "firewall" between seats and the gas tank right behind the seats was 1/2" plywood, and the dashboard was slightly thicker plywood.  I don't know if newer Spitfires upgraded to metal, but the line continued until 1980.

3.  I'm not sure when Saab stopped using little blocks of plywood on a metal rod to adjust the back seat height, on the Model 96, another vehicle that continued in production until 1980.

*which rapidly acquired another name, spelled just like "spitfire" except for the substitution of one letter, right after the "S," that more accurately described it.  I was so glad that he never actually drove that frightening little car on the road, at least not much.

Quote from: Bill Houghton on March 15, 2016, 10:08:57 AM
[snip]
2.  My son briefly (thank goodness) owned a Triumph Spitfire* on which the "firewall" between seats and the gas tank right behind the seats was 1/2" plywood, and the dashboard was slightly thicker plywood.  I don't know if newer Spitfires upgraded to metal, but the line continued until 1980.
[snip]

Not to get offtopic but I have a need to defend the Spitfires. I have one that is basically my DD and I love driving it. Most of the problems I found are more poor repairs than inherent flaws.

J.A.F.E.,

Like all British sports cars, the Spitfires would surely be a barrel of fun.  My attitude toward it may have been colored by my parental worries about my son.

And Triumph was not alone in its awareness of the hazards of gasoline in close proximity to occupants.  My 1972 Chevy pickup has the gas tank right there in the cab, behind the seat.

I did know someone who (after his gas tank fell off), kept it strapped to
the roof for a while before moving it to the back seat and filling it through
the open back window.  Don't remember what make of car it was, but with
that sort of risk tolerance, don't suppose it matters.

Spitfires were Triumph's attempt to copy the Morris Garages Midget, with more rattles included at no extra charge.

As to concerns with plywood firewalls, the burnthrough time on plywood is probably longer than the safe time afforded by a steel firewall.  Wood chars and lengthens burnthrough time.

Quote from: Bill Houghton on March 16, 2016, 12:02:11 PM
J.A.F.E.,

Like all British sports cars, the Spitfires would surely be a barrel of fun.  My attitude toward it may have been colored by my parental worries about my son.

And Triumph was not alone in its awareness of the hazards of gasoline in close proximity to occupants.  My 1972 Chevy pickup has the gas tank right there in the cab, behind the seat.

It was a gentle poke meant in humor. LBCs are not for everyone - my wife for one. I get the parental concern there is not a lot of structure surrounding the occupants. Still, every trip is an adventure.