Many hardware stores, even Walmart sell a closed foam "rod" or "rope" for pre-caulking. It comes in various sizes, (thicknesses) and in rolls. You can buy it by the foot in some places or a roll.

Ace sells a 3/8" by 20' roll for $4.48. Lowes, HD and others sell various sizes and lengths. It's a pretty easily found item.

Frank

Thank you all. I think I now have enough information to complete this task.
Stand by for my next problem. As a single, first-time homeowner there are many. :)
I think attic ventilation may be my next thread. Seriously, thank you.

RE attic ventilation, do a search first, there are many threads on this subject, and you will get lots of background info before you ask any questions, then ask for clarification. I have personally posted several comments on this subject.