It's a very funny name, but as soon as you read it, you can understand the similarity.
It is a three-pronged stimulation: anal stimulation, vaginal stimulation, clitoral stimulation (I distinguish the latter two even though many might think they are the same thing)
So if your partner prefers to focus only on one stimulation, I don't think it's for her.
Now I'll explain the position:
She has to be in a similar position to the doggy style, but the butt doesn't have to be at the top, but quite low. You put yourself under her, your face must be under her vagina, especially at the height of the clitoris.
Then with one hand you put a finger in her anus (or even more, see how your partner prefers) and with the other hand you finger her.
So at the same time you lick/suck the clitoris, you make them an anal finger (I don't know if there's a specific term for this) and you also make them a classic finger.
Why do I call it the mechanic's move?
Imagine the mechanic who puts himself under the machine and uses the other things with his two hands, just like in this case.
I don't know if it's actually a common sexual position/act, I've never heard it before and I wanted to share it with you. In case, I'm sorry.
If you've never heard of it before, and you'll try it, let me know how you found yourself!