Another perspective, I flipped it over so I could paint along the bottom edge. I don't paint the sides of my canvas fully, I allow the original surface to show and the white gesso is a great contrast to my dark background. I mask off the sides and take the background around the edge about 1cm. I used to paint the sides by continuing my painting onto it, however this is now my preferred look. My canvases are 3cm deep, well almost 4cm as they are a rounded edge with the linen I use. My canvases are made up for me @studioartsupplies who do a superb job. I'm currently having a canvas reverse stretched for a work where I'm having the look of raw linen in the background....excited about this piece but starting my heritage roses first.