What type of joints hold bones firmly together without allowing movement?

Fixed joints hold bones firmly together without allowing any movement. These joints, also known as immovable joints, are primarily found in areas where stability is crucial. For example, the sutures in the skull are fixed joints that connect the various bones of the skull. The lack of movement at these joints provides structural integrity and support, making them ideal for the protection of vital organs, such as the brain.

In contrast, ball and socket joints allow for a wide range of movement in multiple directions, hinge joints permit motion primarily in one direction like a door, and pivot joints enable rotational movement around a single axis. Each of these joint types allows for some degree of flexibility or motion, unlike fixed joints, which are designed specifically to maintain bone alignment and rigidity.