Shabbat 60 - No-Nail Sandals

A MAN MAY NOT GO OUT (ON SHABBAT) WITH A NAIL-STUDDED SANDAL

On the face of it - an odd restriction. Would the nails be considered removable ornaments so that there would be a fear of carrying? No, that doesn't seem reasonable. Any nails in a sandal would either be integrated (part of its construction or a reinforcement) or decoration. So what's the problem? And why only sandals, why not other kinds of shoes?

There's a story:

It was a time of persecution and some solders were hidden in a cave. One solder dropped a sandal near the enterance to the cave facing outwards. When the others saw it, they assumed a comrade had left the cave and been seen by the enemy who would attack them at any moment. So they pressed tightly further into the cave. In their panic "they killed of each other more than their enemies slew of them."

(two similar versions of the story are also recounted.)

How did the rabbis respond to the tragedy?

"In that hour it was enacted: A man must not go out with a nail-studded sandal."

This reminds me of the Biblacal story of Jacob who while wrestling with the angel has his hip pulled from his socket - in rememberance of which Jews don't eat the sciatic nerve of an animal. Particular (and pecular) restrictions expalined as mnemonics of significant events.

Perhaps these are folk etymologies but they speak to the way we honor the past.