Literally encastre plástico means 'plastic insert'. That would be a good term to use to describe the plastic piece that holds a product in place inside the box. Another item you might be referring to would be the plastic tie or a zip tie. These look like a thin cord and usually must be cut or untied from the back to allow the product to be released from the package. Also, here are some corrections to your question: When you get a product screw (I'm not sure what a product screw is) and you try to open it you will find the "encastre plástico" that is still locking the product in. It is a small piece of plastic that is often found when a product is disarmed and it is located on the edge of the product body. Its function is to lock one side with the other. I didn't find the way to add a picture for my description to be clearer. I hope you understand me and I would also appreciate it if you would correct any mistakes that I may have made in my description. Hope that helps!