What does the "T" mean on the jigsaw blade?

I have just bought kit of jigsaw blades and they have a T on them with different numbers what is the difference ? And what does the T mean?
Kathy, March 2009


done
It means it is a T-Shank, which indicates it is shaped like a T on the end where it goes into the blade holder.

Don- www.toolsandmachinery.com, March 2009