For all the different techniques around for cooking a steak, one of the quickest, easiest and those still used in kitchens today is the hand trick. Yes, a simple hand trick can tell you how well done a steak is.
The diagram below, a simple graphic design of a hand in different positions, shows you exactly what you need to know for understanding steak doneness.
For example, is you want a rare steak you should leave your hand open and match the touch of the flesh at the bottom of you thumb to the flesh on the steak.
It might seem rudimentary but many chefs still employ this technique for understanding when a steak is at the right doneness.