You've possibly seen Deviant Ollam mention this item in some of his presentations or in this video and this video. This heavy-duty nylon strap includes velcro attachment points so that it is possible to secure a thumb-turn handle on the inside of a door in such a manner that no use of a key or other unlocking token is feasible from the outside of said door. If you want to ensure that nobody will enter a room while you're inside, a tool like this can be a real benefit!
The Red Team Tools Deadbolt Strap also frustrates the use of an under-door-tool in most hotel environments: Normally, even if someone were to use their hotel room's "deadbolt" feature, this automatically unlocks with use of the inside door handle, per NFPA and ADA regulation. Thus, an under-door-tool attack often undermines attempts at better hotel security. However, if the deadbolt is locked in place by means of this strap device, the under-door-attack will fail and there is also no easy means for an attacker on the outside of the door to reach through and interact with or remove the strap, although it affords the rooms' occupants an easy means of removal for rapid egress in an emergency.
Lightweight and an ideal addition to one's travel bag, we're happy to stock this item even though it frustrates the use of many of the attack tools we sell here on our site. :-D
NOTE: While doors can be equipped with a wide variety of lock and handle hardware, there is almost always some configuration of wrapping and attaching that allows the Red Team Tools Deadbolt Strap to work reliably. See the above-linked video for a more detailed explanation of the proper deployment and use of this product.