I made pressfit construction kit in Inkscape. See also User:Frosti/Pressfit
Using cardboard (width 2,5 mm)
Method:
File-> Document Properties -> Grids,
Grid units mm
Spacing X: 2,2 (depending on the thickness of material)
Spacing Y: 2,2 (depending on the thickness of material)
Then I made different kinds of shapes in Inkscape, rectangles, triangles, pentagon and circles. I also unified 2 shapes at time together by selecting them and holding shift key down, then I press CTRL +.
I also made shapes to cut in to the shapes for making press fits. I made boxes with the width of desired press fit. Then I selected the two things and then I press CTRL -.