Answer:
A standard dimension for sandwiches and rulers
You are on an electric train. Which direction will the smoke fly in?
What time is spelled the same forwards and backwards?
What object has keys that open no locks, space but no room, and you can enter but not go in?
This is a shape and a symbol that we literally cannot live without. What is it?
Those with eyes bigger than their stomach will definitely leave the restaurant with one of them. It is named after a house pet as well.