Seb2015 - just what I was going to say - jar openers are useless on most lids on glass jars but great for opening plastic milk containers & smallest bit in middle for lids on fruit juice cartons. 
Ring pulls I find often break when you lift them away from tin so it's back to faithful tin opener 
Any advice on grandchild/granny relationship problem
or that they could cause such sickening pain!

