Krul, 24, revealed Given and Harper spent time showing him the ropes of how to be a top keeper - literally.
He said: "Shay and Steve told me to hold my arms straight in front of me, to gain more time to react in a one-on-one situation.
"On a certain day they decided to force me to do it in a more extreme way. They pulled my wrists with a rope on training.
"That's how I learned to use the right posture. It really helped me."