You may want to draw this line in pencil the first couple of times. Use a T-square to make sure the line down the middle is at a right angle to the base of the triangle. This fold is to form a crease that will be important for the following fold.
Be careful to line each fold with your imaginary pencil line. Make sure you keep each fold very tight and at the same angle. If the folds start to slant upwards, instead of staying aligned, the claw won’t be as sturdy.
It may be a tight fit at first. The tighter the fit the more likely the claw will stay on your finger.
Sturdier paper will increase the the durability.
This fold is to form a crease that will be important for the following fold.