I am a big fan of Blitzkrieg-Commander (BKC) and Cold War Commander (CWC). BKC is what got me back into WWII wargaming since playing Command Decision and Rapid Fire years ago. I've been playing BKC/CWC since probably 2004. I have not played as many games as other people, but it is my WWII/Modern ruleset of choice.
This post shows my latest 10/12mm trenches for BKC. The size is based off the BKC version 1 size. They are made from thin birch and balsa. The picture below shows the progression of the construction. They will be used by the Germans defending against a Canadian attack in Normandy.