Rails come in more than 2 weights (dimensions) IIRC. Narrow gauge railroads typically used a lighter rail. Per Wikipedia there were dozens, rated in pounds per yard. I remember as a kid my dad's shop had a short section of rail that was used as an anvil and we tried picking it up when we visited. I was maybe 4 when I was finally able to lift that one foot chunk by myself.

Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.