My custom font is not appearing, and I can't figure out why

For whatever reason, this is not working out and I cannot figure out why.

This is in my custom CSS file.

@font-face{ 
    font-family: 'AAS';
    src: rl(/path/to/user/themes/quark/fonts/aas.ttf) format('truetype');
}
body {
  font-family: 'AAS', sans-serif;
}

I have also tried

 @font-face{ 
    font-family: 'AAS';
    src: rl(../fonts/aas.ttf) format('truetype');
 }
 body {
   font-family: 'AAS', sans-serif;
 }

What am I missing? I have cleared cache and what not, but I am still striking zero.

src: rl()

? You sure? 🙂

That is why I tried the full link. I'm sure.

What full link? Does src support rl()? What is this rl() at all?