It's gotta be a fake body or prosethesis on his side, but even in HD I can't see it
I understand why there are (obviously false) rumors that Clay allowed an actual surgeon to implant the sword in him
It was revealed in the 2013 documentary...
https://pbsinternational.org/programs/excalibur_behind-the-movie/
Neat documentary, thanks!
I couldn't view it on PBS, but found it on Vevo
I actually couldn't find anything referencing the stab wound directly, unfortunately
It did inspire me to examine my HD version, though, and I can now pretty much see what they did
The sword Clay is holding has a retractable blade. As he rolls back, he hides the lower portion (which, impressively, remains properly aligned as if it's really running through him). Then, in just two frames of my HD download, you can see the pointy end coming out of the main blade.
The only thing missing, and it's only evident now in HD, is that Clay has no wound where the sword came out, just some blood. As a kid seeing it in theaters and out of the many, many times seeing it on HBO, I'd always thought there was a clearly visible slit where the blade came out, but the HD version makes it clear that there's just surface blood.
It's an incredibly well done f/x gag
You're welcome. I was sure the description was in that doc, and I can't find it now.
This is a similar explanation though - https://www.reddit.com/r/movies/comments/kdz0ip/in_excalibur_1981_when_lancelot_pulls_the_sword/
In case the page plays up - https://pixhost.to/show/147/195816503_in-excalibur-1981-when-lancelot-pulls-the-sword-out-of-his-side-i_-www-redd.jpg