Can anyone help me identify this novel. It’s similar to “Lest Darkness Falls,” (unless it is as I haven’t read in decades) where a person attempts to use his knowledge to change things, but in this novel, he fails as his knowledge isn’t applicable. It might have taken place in medieval times. I think, if I remember correctly, he knew how to build metal bridges, but knew nothing of the stone bridges of the time. Any help would be greatly appreciated.
There’s time travel novel called “The Iron Bridge” but the main character is a woman http://david-morse.com/ironbridge/
It’s The Man Who Came Early by Poul Anderson. Not long enough for a novel, usually found in collections.
edited to add a link
It’s a great story and I especially like the framing device of an old Icelander telling the tale.
I came across it in this collection of The Best Time Travel Stories of All Time.
It’s not the one you were thinking of, but if you like that sort of thing, you might enjoy Leo Frankowski’s The Cross-Time Engineer.
Yes. That does sound like the OP’s story.
I think “The Man Who Came Early” is it as well. Thanks Bill Door.
Also, thank you Andy L. and bibliophage for the other suggestions. I’ll look them up.