Using images for borders or backgrounds to surround an element?

[SamA74]

@Linda_A

I am trying to apply it just vertically, and I end up with gaps, presumably where the corners are skipped

Maybe use an ordinary tiled image if you just have vertical borders.

@Linda_A

applying the borders messes up the placement of the sidebars. Is that because the border adds width?

Yes, borders will make your element bigger according to the standard “box model”.
You can change this with box-sizing: border-box