Furniture needs to be attached to the wall, but my tenancy agreement doesn't allow it
As a landlord I would say it's not the putting holes in the walls that I don't like, it's the leaving holes I have a problem with. As long as it's a normal sheet rock and paint wall, not paneling, finished woodworking, or masonry, that's a different story. A few holes for a noble cause (keeping your bookshelf from crushing a toddler for example) is not an evict-able offense, unless your landlord is out of his/her mind, so the worst thing that can happen is getting dinged on your damage deposit when you move out. And if you properly patch and paint your holes that won't be an issue either. I'd still ask first though just to be safe, we landlord's hate the old "ask for forgiveness instead of permission" trick:)