I think you're referring to the two slots on the back of the mounting bracket that slide over the attachment pins (tractor anchor pins) that allow you to raise the mounting bracket and engage the Snap Fast pins. If that's correct, here is my method for my '87 446 with N46 deck (LH discharge). I let the tractor do the work. After driving over the deck, I attach the Lift Links on each side and partially raise the deck so that the mounting bracket is in position to easily slide over the attachment pins and then the Snap Fast pins are easily engaged with little effort. It may be a trial and error effort at first to find the right height with the lift links, but it sure beats trying to "horse" the deck and bracket by hand.
I'm getting to that age where every year things like wheel weights and 6 gallon gas cans get heavier, and attachments like decks, snowcasters and tillers are more burdensome. That's why I use a lot of movers dollys and other wheeled contraptions to put attachments on.
Here is a pictorial for removing/attaching of my tractor and deck that I made up years ago in case my sons needed a quick reference:
Bob