does the mirror COMMAND work in 2.47

i select the mesh- in edit mode-press M and and and nothing!

The M-key mirror is more of a “flip” and it works only on selected areas of your mesh, and you need to specify which direction x,y or z. (hit X, Y or Z after hitting M). If you select the whole mesh of an arrow, an M-key type mirror would result in it pointing the opposite way.

More likely you are wanting the mirror modifier, which is capable of creating “the other half” of a mesh, so that when you edit the right shoulder, the left is also adjusted… is that what you’re after?

"is that what you’re after? "
Exactly correct
how do i do that?

Mirror modifier…

I would write a quick to torial but I’m wanting to rest for the night.

I have dialup so won’'t check the content; let me know if this video answers your question:

And this:…lender-176959/

that tut is excellent - a different way to mirror.