This is a wall mounted isle that can be sized to any length you want. It uses simple and cheap parts easily found in any hardware store with couples of grams of filaments. 

What you will need :
x2 Square aluminium tube 1.5" x 0.75"
x2 M12 RivNut 
x2 M12x45 Bolt ( or thumb screw )
(optional) 10x1.5mm Rubber strip
(optional) LED Light (https://amzn.to/48Xz5Pe)

Step 1 : Insert the RivNut inside the "Part2". It should be a press-fit inside the part. If ever you find the fit too loose you can add a drop of glue.

Step 2 : Screw down a piece of wood onto the "Part1" by the back trough the holes. The length of it is arbitrary and can be cut at any length depending on your canvas size or preference. You can also glue down the rubber strips into the groves. That will help with friction to keep everything in place without tightening to much the knobs. 

Step 3 :  Insert the two square tubes inside the "Wall_Mount" parts. It should be a tight fit because nothing else hold the in place. You might need to bring the mallet ;) !

Step 3.5 : Install the assemblies of "Part1" and "Part2" onto the tubing before mounting everything to the wall. You should have two copies of this assembly (one for the top of the canvas and one down).

Step 4 : Mount it to the wall and paint :D !