This is a strap to support instrument cases when placed vertically on trains, etc. It is compatible with cases that have a handle on the top (see photo). You thread the strap through and secure it with a buckle. I made this because holding both a handrail and an instrument is inconvenient as it leaves your hands full. The length is adjustable. It doesn't take up much space, so you can leave it attached. For a person 170cm tall with a violin case that is 82cm high, there was 5cm of extra length on the strap. Please use it only as a supplementary support. This is handmade. It is a product of an amateur, but thank you for your understanding.