Dragonwood Design Studio - Why the Rockler Dovetail Jig Needs a 1/4 Inch Shim for Through Dovetails

I couldn't find any videos on why the Rockler dovetail needs a shim on top of a piece of stock. The top piece isn't cut, so why do we need this shim?
This video shows why, but still don't know why this needs to be set up this way. I think a thicker backer plate could be used to prevent tear-out from behind. Watch as I explain what is going on as I cut a test piece.

[@Hooolia2214]

Thank you. i just got a Rockler jig and just starting to learn so thank you for the info.

[@colemine7008]

thank you for this, I just picked up a rockler jig to play around with

[@DragonwoodDesigns]

Glad I was able to help. Any questions, let me know.

[@bunnybigley6531]

That is a great video, keep up the good work. Looks like that is going to be a fun treasure chest to make:)

[@BryanWilliford-c8d]

Just recently got this myself what sort of hit did you use for the tails was it just a straight cut bit?

[@javiercastellanos3296]

Porque no tiene traducción?

[@donttrustnobody]

Hello sir, You’re supposed to put the shim under the material not on top.