Connect part faces together?

I want to know how i can connect two part’s faces together as in one part scales to the edge of the other one’s face.

Example:
image

Any help is appreciated!

There’s not a lot of information to work with, do you have a script or anything?
(Also retitling your most to be more concise may bring in more help)

i added another image to show what i mean, i want them to connect so the wall isn’t open.