What is the fine-grained topic of the following text: Able roller shutters are constructed from galvanised steel lathes/slats 50mm flat or 75mm curved in either 20 or 22 gauge thickness dependent on space/span to be covered, interlocked together to provide solid vandal,theft proof barrier, mounted with in a 3mm and 6mm thick steel sections which are securely connected to the building, supported by a counter balanced roller spring mechanism or optional electric motor housing designed to offer easy roll up and roll down of your security shutter. Only return the topic.
Construction and Design of Able Roller Shutters