Time for another random observation about the English language: the difference between one-handed and single-handed. I noticed this when I was looking at the kind of play (such as Educating Rita or Red or Talley’s Folly) which has only two characters (or sometimes two actors playing more than two characters) (or, I suppose, fewer) and which is known among theater folk as a two-hander. This despite having (most often) four actual hands divided more or less evenly among the cast. I assume that the metaphor is drawn from card games. A play with three actors is sometimes called a three-hander, and a play with one actor is called a monodrama.
But I did recently see such a play referred to as a single-hander and while I deprecate such a usage, it is true that a monodrama requires the actor to present the performance, well, single-handedly. But not one-handed.
To do something one-handed or (with one hand) implies, I think, either that the thing is easy or that you are peculiarly skilled at it. At least, it implies that the person is not putting forth full effort. I put it together with one hand, he says with an insouciant grin, and she is ever so impressed, she is.
But to do something single-handed implies a tremendous effort. Did you put it together single-handed she asked shyly, and he smiled quietly to himself.
I had never noticed it before, but I think it’s fair to say that single-handed and one-handed are, if not technically antonyms, at least pretty close to having the opposite meaning in idiomatic use.