Off Topic: Switch box

[Koot <dowd@xxxxxxxxxxxx>]

A bit off topic, but I'll give it a bash :-)

I need a switch box for 3 of my pc's to use one monitor, keyboard and
mouse.
Got one from Cable link, but it did not work as expected (blurred
screen, lost the mouse and keyboard when switching between pc's and so
on).

So now I am thinking off "building" one from a diagram (if it is not
going to work as expected, then I can just as well do it my self).

Now the question is, where can I get a diagram for a "good" switch box?
A switch box in "kit form" is preferred, but I don't think that is
available locally.

Thanks