Shield in the context of a porn video tag typically refers to a sexual act or position where one partner protects or shields themselves from their partner's body, often during penetrative sex. This can be done using a variety of physical barriers such as pillows, blankets, or even specific items designed for this purpose like sex wedges or cushions.
The purpose of the shield is to provide comfort and control, making it easier for participants who might be experiencing discomfort, pain, or lack of control during intercourse. This can also allow for a more enjoyable experience by providing a buffer between bodies that may not naturally align or fit well together.
However, in some cases, 'shield' can also refer to the act of protecting oneself from an unwanted sexual advance or situation. In this context, it would be used by someone who is consenting to sexual activity but may want to establish boundaries or safeguard themselves against any potential harm.