Sneakpeekit is a free library of printable wireframe templates: grids, browser frames, and mobile device outlines as downloadable PDFs, released under a CC BY-NC-SA license and downloaded over 1.5 million times.
The device-outline templates (phones, tablets, multi-browser layouts) save the tedium of hand-drawing screen frames, so paper sketches focus on layout and content instead of getting the bezel right.
Good for the same early, paper-first sketching stage as Sketchize: pick whichever template set's device frames and grid style you prefer, since they solve the same problem slightly differently.
Non-commercial license (CC BY-NC-SA): fine for personal practice or internal sketching, but check the terms before using it in anything client-facing or commercial.
Printable grids for sketching out wireframes on paper.
