I stumbled across a method for holding the balance cock firmly in place while re-installing the hair spring. I used a heavy tap wrench with a tapered steel rod and placed the balance cock on the tapered rod with the jewel facing up. I then stretched a thin rubber band from under the tap wrench over the top of the balance cock. Using a heavy tap wrench made a very stable base that held the balance cock firmly so I could use both hands to install the hair spring. This is the first time I ever re-attached a hair spring and was surprised how easy it was without having to also hold the balance cock. I know it looks simple but it worked for me. I got the basic idea from Bob on the watch video and then added of few of my own touches to make it more stable. Enjoy.