If you have ever run out of saline for your central lines, this simple trick will help you out:

1. Hang a saline bag before getting sterile

2. Open IV tubing onto your sterile field. 

3. Once sterile, hand off end of tubing to spike bag

4.Viola, 1 liter of saline at your disposal!

....difficult to imagine? Don't worry, this video explains it all.