Usually TSA have guidelines as to what's allowed and what's not. But on the official website there should be a list of what can and cannot officially be taken on a plane, but "every airport is different".
At the airport I worked at, all blades irregardless of size are not allowed, but they allow 4 inch scissors on the plane



, as long as they aren't knife-tip scissors or can be separated at the fulcrum (rivet).
You can't have a swiss army knife classic, but you can have a 7 inch crochet needle.
All tools had to be 7 inches and smaller, so a super long screwdriver is allowed...
Besides all that
I never needed a multitool on an airplane, never needed to screw. Snip, or pry anything, just waiting until I land, which is essentially what people do. I did run into a few passengers who would go so far as to remove the blade from their Swiss army knife.