When I spoke to my FLO he said my garage (integral with the house) was OK. No need to bolt to anything (as wirh a gun cabinet) - just a chain from box to water pipe or similar accepatble - just so's no-one can pick it up and walk off with it easily. Box to be locked. No need for any special colour or wording on the box. Check with your own FLO though - as we know, each area interprets the rules differently.