How do you divide a rounded rectangle using pathfinder using Illustrator?

Question

I'd like to create a rounded rectangle that's cut evenly in half with the flat edge in the middle left open (#4). Once I created my rectangle using the rounded rectangle tool I created a line using the line segment tool in order to divide it in half (#1). Then I'll select both the line segment and the rounded rectangle and use the pathfinder divide tool. This causes the space in between to be filled with a black line (#2). Once the two halves are ungrouped the solid black line stays as part of the individual shapes (#3).

Answer 1

When you create a rounded rectangle you will have a path that looks like this:

Go to Path> Add Anchor Points which adds anchor points exactly between the existing anchor points:

Then choose the scissors tool (keyboard shortcut is c) and click on the middle top point and the middle bottom point. This will "cut" the path at those 2 points.

Then simply move the paths apart and you will have what you show in your image # 4.

Answer 2

Seems to work exactly as expected for me in CS6.

Maybe Adobe broke it in newer releases.

Simply use the Direct Selection Tool (white arrow) to select and delete the new verticals.