Due to the extra stress towards the edges of a windshield, breaks tend to spread rather quickly. However, sometimes a rock hits close to the edge, even on the frit, and leaves a repairable break. This poses and additional challenge.
Breaks that have a leg that terminates at the edge of the glass have an extra opening to the environment in addition to the pit. The crack at the edge will allow air to enter into the break and eliminate our ability to form a vacuum. There are ways to overcome this problem.
Method #1 - Many modern windshields have exposed edges rather than mouldings that cover them. This allows access to the opening of the crack itself. First, place a small amount of Crack Filler into the very edge of the crack and massage it into the crack wearing a Nitrile Glove. Second, take a drop if Pit Filler and coat the same small area and edge of the glass, then cure it as normal. Now, you have sealed that open area and can perform a repair as normal. (We have had them so close to the edge that we have had to cut the rim of our pedestal to get it to fit! There's another tip.)
Method #2 - If you do not have access to the edge due to a moulding, perform a standard repair but skip the vacuum process and go straight to injection. Sometimes this can be done when the crack that hits the edge is even longer than the pedestal radius and shows. If so, this is great. Allow the resin to flow until it reaches the edge. Then allow the visible area to cure while leaving the pedestal in place. Once it has cured, restart the process, this time using the vacuum steps as well. If you must remove the pedestal to see the crack, this is fine. Just be prepared and work quickly to avoid unwanted curing. Remove the pedestal and cover the enter area except for a small portion by the edge. Cure that portion. Apply another pedestal and repair as normal. If you work quickly, you will avoid a chain reaction cure to the covered area.
With this and all extreme situations, be creative and inventive. Use all your resources to try and solve problems. And, please share your solutions! We have been doing this for decades and still learn something new every day.