Align outside border to grid

i hope it is no dupe. If it is then i'm sorry..

I simple want to create a textureatlas for libgdx.

Therefore i try to wrap all my 2D images/textures into one Image and select my desired images within the atlas at runtime.

In Inkscape I setup up a grid with many tiny rectangles which are representing the corresponding area of each image, respecting an aspect ratio of 4:3.

But i start to struggle with a simple pause symbol.

As soon as i stroke the path representing the border of the rectangle i notice that the border breaks out of the corresponding area into the area of another image.

How can i align the outside border to the grid independently of the stroke width.

Any help is appreciated.

Thanks in advance.