The muscle you are referring to is likely the tendon of a muscle, specifically in a context that may relate to muscles like the digastric muscle or mylohyoid muscle. However, a common example of a muscle that is often described as being attached at only one end would be the tendon of a muscle, as tendons connect muscles to bones but are often considered as having one fixed attachment.
In terms of function, muscles that have attachments primarily at one end (like some tendons) allow for movement of bones through contractions. This enables actions such as lifting, pulling, or pushing, depending on the muscle's location and function.
However, if you are specifically looking for a muscle that behaves as if it has one fixed attachment point, you might mean the latissimus dorsi, which can function in a way that affects movement while the origin remains stable.
If you could provide more context or specify a particular muscle or movement, I would be happy to give you a more precise answer!