Bootlint is the official Bootstrap HTML linter tool. It automatically checks for several common HTML mistakes in webpages that are using Bootstrap in a fairly «vanilla» way. Off-canvas Build a toggleable off-canvas navigation menu for use with Bootstrap. Although the image was pretty useless in this case (nothing was changed about it), this page should’ve given you a general idea of how Packer works, what templates are and how to validate and build templates into machine images. Add custom media queries to change the grid size breakpoints for print media only.