Non-restrictive bondage
From wipipedia.org

Non-restrictive bondage is any form of bondage that does not of itself restrict the captive's freedom of movement or ability to see, talk or hear. Examples include:
It may be used to intensify the bondage experience. It may also become restrictive if it is attached to other bondage; for example, if a crotch rope is attached to a wrist tie it restricts movement of the arms.
Similarly, some items of SM equipment do not of themselves restrict movement, although some can be used as anchor points for bondage. Examples include:
- Bondage belt
- Butt plug
- Dildo
- Collar
- Harness (some types)
- Nipple clamp