What are you using to attach diy inserts to systainers?

[mickmick]

I bought a couple of systainers I want to fit out with some hand tools and bits and bobs. I have seen some really cool custom lid inserts that hold chisels or screwdrivers.
How are people attaching these diy plywood inserts to their systainers? Some look like they are screwed in, but I can't see how that would work. Anyway your ideas greatly appreciated.
example of kind of thing I'm thinking of:

 

[Distinctive Interiors]

As in your picture, there are 4 holes in the lid of a systainer that will allow you to fix a ply insert to.
They are about 5mm dia if I remember correctly. Usually, the card insert fits in place using the same holes and the card is held in place by means of white plastic inserts.....

 

[Joort]

To attach a lightweight "cushion" (made of plywood and cork) to the lid, I have inserted a simple wall plug (cut to size) into the existing holes. Filling them up with wooden toothpicks to make it snug. Works.
For your application (more weight) you could consider inserting a round nut that you heat prior to inserting. Or use some glue. You can then use a bolt to hold your plywood.