The seat has remained in the truck since Sunday afternoon, and as it was clear and sunny all day long today I thought maybe the plastic--thus warmed--would have softened a bit.
Well, it didn't. But I discovered something nonetheless.
You see, after it didn't work and didn't work and didn't work--the same way it didn't work previously--I set the gun in the middle of the seat bottom, leaned on it with both hands, and actuated the lever...and it drove the staple all the way in.
It develops that the problem was with inertia. Before, I would hold the gun firmly against the work and pull the handle, but no matter how much muscle I put into holding that thing against the work piece, it was still moving (however slightly) when push quite literally came to shove.
If I leaned against it with as much of my upper body as possible, the staple gun couldn't move, and thus it drove the staple all the way in.
But I discovered this shortly before I was going to have dinner. I was feeling a bit hypoglycemic, so I brought the stuff inside the house with me and had dinner, intending to go back to it later.
That was around 5-ish. I brought my bowl of ham and bean soup into my room and sat at the computer and played WoW; then I watched anime.
And it's now 1:30 and the seat's still not done.
Well, it's supposed to barely reach 50° tomorrow--today--Thursday--so it's not like I'd be doing a lot of riding anyway. I can get the seat put back together and do some other minor chores, and when it warms up this weekend I can ride the motorcycle then.
That's fine with me. There's no rush.