Making Guides at an Object's Borders
This is a simple script whose idea comes from imagining that you have first created an object on the page and now you want to set some guides at the borders of the frame as a reference for other page content.
Usage is quite simple. Just select your object, run the script. Any pre-existing guides are preserved, so you can repeat this for other objects on the page. If there are any guides you don't want to keep, just slide them off the page – make sure your guides are not locked.