In my latest conquest of DIY i.e. Do It Yourself mission, I wanted to learn about a SCREW and not just our simple screw but most recent addition in the family of screws i.e. Expandable Screws. I found out recently that the air conditioner on my second floor window is placed using these screws. So, when I started researching more I learnt that these screws were specifically designed for installing heavy objects on concrete walls or for masonry purpose. Some common examples are installing dish antenna on the roof, holding the shade to cover your car or open area, tightening a rope to climb the wall etc .A normal screws gains their capacity to hold loads  by creating an interlock with the part in which they are inserted. For example a screw is inserted in a wall or in a wooden plank etc.