Basically, the cardboard on the back of writing pads or in retail packaging. No tagboard handy? Use brown poster board!
tag Pop Goes the Page
Kansas State players eat edible Pop-Tarts mascot after bowl
LEGO pop-up bar, The Brick Bar is coming to St. Louis
Picture Book Projects, Pop Goes the Page
Class 7 Radioactive Placards
Pacon Premium Tagboard Paper, 50-Count, Brights Assorted, 10 Colors (101164) : Office Products
Tag Board United Art & Education
3rd Grade Art Lessons – Art with Mrs Filmore
Canson Comic Book Layout Pages
Cassie Stephens's Blog, page 7