Reflections on the installation of carpeting

Someone decided to carpet certain rooms in our house in about the 1960s using the following guidelines:

1. Staple the pad down every, oh, 4 inches or so THROUGHOUGT the entire space. Just in case the house is located directly on the freaking San Andreas fault and you're concerned the padding and accompanying carpet will shift wildly.
2. Put the tack strip down with sinker nails every two inches, and then when you run out of sinker nails, look around to see if you've got any screws. Those'll work, right?
3. Lay down the tack strip in varying lengths, from 2-12 inches, even if longer pieces would easily fit. Those 2-inch lengths were leftovers and wasting them would be a pity. Never mind that they reduce to splinters when some poor schmuck in the future tries to pry them back up.
4. Once the carpet is tacked in, be sure to glue it down at the thresholds and then staple through the glue. You don't want that pesky carpet popping back up on you!

I spent far too long ripping up a 4x4 square of carpet today (in our upstairs small hallway). And then, when I finally got it pulled up, I discovered something not-so-pretty. Something that deepens the mysteries of our little farmhouse. There is a large -- about one inch wide -- slit cut into the floorboards, extending about 2 feet out into the middle of the hallway. It doesn't seem to be coming from or going to any particular place, and the wood all around the slit matches what we've got elsewhere in the hallway and throughout the house. So I can't for the life of me figure out why exactly it's there. The hallway floors definitely have indications that they weren't always carpeted, so I can't imagine the slit was always there. It's weird.

Hmmmmmm.