EMI/EMC shielding: Probable strategies

Hi,
I am trying to configure a module to have a compliance to EMI/EMC standards.
I find that there is leakage occurring from the module. The probable source of this leakage seems to be the box joints and the bolt holes.

I am looking to know the following:

1) How can I go about reducing this radiated emission just by the improvement of the chassis design? Light weight solutions would be the preferred.
2) Any strategies, materials and best practices I could follow. Suggestions really looked forward to.

Also, any handbook suggested for going about this analysis.

Best
Guruditya

You need gasketing material but i do not know what material to use. Google for this.

EMC gasketing material

There are many vendors someone should be able to help.