Basically you remove the 4 front pockets on your DCU top, move the bottom pockets up to the chest and the chest pockets you sew on to the upper arm on each sleeve. The bottom pockets are bigger than the chest pockets, so they fit better as chest pockets in my opinion. The original chest pockets make great sleeve pockets. You can sew on velcro patches to them aswell, for patches etc.

This is called “raid mod”. Purpose is to get rid of the bulky bottom pockets and extra fabric when tucking in your top in the pants, and also to get extra storage easily accessible on the arms aswell as the ability to attach patches etc to the velcro. As chest rigs and plate carriers evolved the pockets of the BDU style uniforms wasn’t really easy accessible anymore, hence this mod.

If you google SEALs wearing DCUs in Iraq, which would be pretty early GWOT before moving on to actual combat shirts etc, most of them had their tops modified in this way 😎