When uniting shapes, strokes off set creating a bump in the newly created object

[teachertrev]

Can't get them to line up uniformly. When I hit unite in pathfinder, it also creates a bump. I'm sure this is a very common problem, and I'm hoping it's one of those that requires a simple solution like modify a preference. Learning this for my students to help them. Thank you. 

[sishamIAGD]

Looks like your original doesn't line up, so if that isn't correct before you unite them then it will be incorrect in the united version. What does the 2 shapes look like when you preview in outline view? do the 2 corners match up exactly to start with?

[teachertrev]

In outline mode, you can't get them to line up. It always forces my line over to the right or to the left. 

[Ton Frederiks]

If you can't get them to line up, maybe some Snap To option is preventing that (Grid, Pixel).

[Doug A Roberts]

When you say you "can't get them to line up uniformly", what is preventing you achieving that?

Is this a stroke or something outlined?

Are you using smart guides?

[teachertrev]

Just shapes with a stroke applied. Smart guides is checked. The strokes is applied the same to both shapes. When you try to line the strokes up though, they just won't. Smart guides is helpful, so I would imagine you could still do this even with smart guides on. 

[teachertrev]

With the move tool, when you try to move it to the line, it sort of jumps. It gets close, but doesn't line up exactly, making it slightly offset. Thank you. 

[Monika Gause]

Is align to pixels turned on?