A Hardiflex screw is commonly used on hardiflex boards. It’s also called window screw. It’s a special type of self-tapping screw because you may install it without plugs. It has either a flat or cylindrical head depending on the aesthetic and the window frame materials. 

Similar with bolts, screws are also a major category of threaded fasteners. Screws and bolts share a lot of likenesses such as being made of metal and being characterized by a helical ridge. They are both used to fasten materials by the engagement of the screw thread or the external thread with a similar internal thread in the matching part.

Truly, screws and bolts are hard to differentiate with the naked eye. They are both threaded materials and have a head for tightening the fastener, but the most obvious difference is that a bolt is not usually threaded all the way along its shank as it has a plain portion. On the other hand, a screw is threaded fully to the head.

Generally, screws don’t need nuts to get fastened. They become secure by being tightened into the hole using a screwdriver. Screws are usually shorter than the width of the material being screwed and don’t protrude on to the other side.