Note: This can get flagged with going through security, so you may want to put it in an easily accessible place in your checked bag to be safe.
Promising review: “I travel a lot for work and usually take a lot of measures for extra security, such as keeping the luggage roller in my room all week and rolling it in front of the door. It was large and cumbersome, but with this gadget, it’s great! You can use it on almost any door and works better than the makeshift ‘fork’ one. Frequent traveler or not, this item offers peace of mind which can prove invaluable while away from home. (I can even use it on my door at my house!)” —JizzerJittery
Get it from Amazon for $11.99 (also available in two-packs).