Good step-by-ste-tutorial for resizing borders, where?

ok, i´m sure alot of other people been asking this, but need a really good tutorial regarding resizing borders. and i don´t mean them tutorials with complete code and graphic you can download, i mean a step-by-step-tutorial. just downloading codes doesnt make any sense for me :frowning: i would like to understand as well.

thanks! :toad: