Underprops are support structures or devices that are used to hold up or strengthen something that is weak or in danger of collapsing. There are several synonyms for underprops, including buttress, brace, truss, bolster, shore up, reinforce, fortify, uphold, and maintain. Each of these words has a slightly different connotation and can be used in different contexts. For example, a buttress is often used to support the weight of a building, while a brace is used to hold up an injured body part. Regardless of the specific word used, underprops are essential for ensuring the stability and safety of anything that is at risk of collapsing or breaking.