Looking for a tool ( oohharrr )

That YouTube vid got me thinking about some stuff, and I was wondering is there’s a tool that would cut a groove around the inside of a slice of ally tubing or U shape? I want to be able to cut two groves so I can slide a piece of thin plate along them. Very similar to the old wooden sliding top pencil case. I think they are called runner groves? The grove would only be 2 or 3 mm deep and about 3-4 mill tall. More than likey it would look simaler to a dremil saw attachment .. not sure but I dont seem to be able to get the search right for one on google.

Tee slot cutter maybe.

Tee Slot Cutters - Arc Euro Trade

Or perhaps a slitting saw.
Slitting Saws - Arc Euro Trade

Great answers , neeeded to know what to look for and think I've found it 3mm T-slot this should work side on to cut out the slot perfectly !