Does anyone know if there is a way to mirror a model (mdl)? I have a weaponframe of a hand with a hammer, but it is left handed. I need a way to mirror all frames so they become right handed. 

You can do that in QME.

Open the model. Change into Object tools editing mode, and make sure that "root" is selected by clicking in an empty space. Change the settings at the bottom to:

Scope All Frames
Model Relative
Subject Object

Type -1 into the Y box of the Scale control and press enter. Your model will be mirrored, but the triangles will be backwards. Change to Triangle tool editing mode, select all the triangles, then right click and select Flip Triangles. Now the model should be mirrored as desired. 

Thanks Preach!
I guess I learned something new with this program again. Saved me a lot of work. 

Cut from .map
{
"classname" "misc_model"
"origin" "768 192 20"
"mdl" "progs\misc_bonepile.mdl"
}

and model in TB visible as model, not box i.e. path is correct. But after compiling quake engine report
Mod_Load_Model progs\isc_bonepile.mdl not found
.
.
Here list of all misc_models.
Yes is cutting first character in model's name. Putting model in sub-folder causes the same in addition is cutted first symbol of subfolder too.

My system: Win 10 TB 2021.1 ericw-tools-v0.18.1 / tyrutils-0.17-win64 QS 0.94.2 QSS 14.10.21
Few days ago all worked fine and nothing obvious where changed. 

and ad_1_8.fgd bundled entities enabled in TB 

---- LoadMapFile ----
line 27: Unrecognised string escape - \m

and this string is:
"mdl" "progs\misc_bonepile.mdl" 

instead of /
God damn! 

Hah, that’s what I was going to ask about :) 

it seems a bit antithetical to the kill count to do this, but if I wanted to decorate a part of my map like a scene and have a passive Fiend just standing there, could I easily do this? I am basically looking for a way to make an enemy unaware of a player, as if they are notarget'd. thanks! 

If you're mapping for a mod, cleanest way is to just use misc_model. For vanilla there are a couple of hacky ways.
One is to use a func_illusionary point entity and set its "model" to "progs/demon.mdl", and then "frame" to the desired frame ("53" for a dead fiend). However you'll need to precache the model by using another live fiend somewhere else, and you won't be able to rotate the model.
Another way is to add a regular fiend and set its "nextthink" to "99999999" (see also). It will be frozen in its first frame and will contribute to the killcount, but won't be shootable.
Finally, you can just add a fiend and surround it with a func_wall made of skip. 

also check out this thread for many map hack techniques: https://www.celephais.net/board/view_thread.php?id=37116&end=25 

thank you both!!