The only time i hear japanese say とお is phone numbers (like ひゃくとお番)
What are other common usages of とお?
I've also got a sub-question, but don't want to post a new thread so i'll just ask here. As i understand it -つ counting is only used from 1 to 9. What if i need to use it further? (like if i don't know the correct counter for some stuff) For now i stick to 個(こ)like じゅうにこ, is there any other way?