I've always had trouble understanding how people could have trouble doing something as simple as turning a knob with either hand.  It's not quite as challenging as writing or fretting guitar notes/chords or whatever.

Speaking of guitars, why do right-handed people prefer to use their left hand for fretting guitar notes/chords?  Seems like strumming or even most picking (unless you're Eddie Van Halen or something) would be easier to do with the non-dominant hand than fretting.

I'm "left-handed" but I do lots of things right-handed too.  I only realized not that long ago what resulted in my doing some things left-handed and some things right-handed. I don't have any recollection of making those choices.  It turns out that anything that required special "left-handed" equipment is something I do right-handed, but if no special equipment was required then I chose the left-handed approach.

Since you don't need a special left-handed pencil, I write left-handed.  Similarly with swinging a baseball bat.  But I throw right-handed because otherwise I would have needed a special left-handed baseball glove (which is worn on the right hand).  I use a computer mouse right-handed and I bowl right-handed as well.  I shave left-handed.  I play drums open-handed or right-handed (you can setup any kit to be left-handed but it's too much hassle if you're playing a kit that's already setup).  For some reason everyone seems to get by with the same pianos, rather than anyone using a piano with the bass notes on the right side . I'm not sure what to call my knife-and-fork technique, since that seems to vary more by country than whether you're right- or left-handed.