After doing some cleaning over the weekend, I found these left to us from the prior owner of my home. I've never come across these before, but they look to be lag screws within some sort of hangar or mount. Can't say I've ever seen these during a trip to the hardware store, nor can I find any location in my home where they're actually in use. Frankly, I'm baffled.
What are these, and more importantly what are they used for?