Stephen_B wrote:
I have toddlers (need I say more?). I would like to anchor a
freestanding bookshelf to the wall so that it does not topple over in
case any of them have climbing aspirations.

The L-bracket works well for shelves in which the back is open, but I
was hoping to find some kind of canvas strap to use for my closed
shelves. Any suggestions?

Only the most modest of anchoring is necessary. If you look at the mechanics
involved - or even try an experiement - you'll see that a mere string
attached to the top of the bookcase and anchored to the wall via a picture
hook will suffice.