>How are sizable forms that adjust form object sizes implemented? I'm talking about the forms with the "///" in the bottom right corner.

There are several Autoresize classes in the Files Section, they may automatically resize all form controls once Form is resized.

(in no particular order)
File#1374 AutoResize resize any object in the form
File#645 Resizing and Moving controls at run time
File#720 Form Resizer
File#749 vresize.zip
File#307 Autoresize
File#9297 Autosize