Corel Power Clip is pretty cool:
Put your image and text on the page:
Select your image and go to Effects>Power Clip>Place Inside Container:
Then choose your container, text in this example:
It's really just a shortcut to producing a clipping mask effect, so older versions...
Screenprinting on tshirts generally has a lot of dot gain as the ink spreads and doesn't need trapping, but if you sometimes have gaps between two adjoining colours you can make life easier by adding a trap.
Traps go by a variety of names - overprint, bleed, choke etc. They all involve...