This is a rail hook for hanging hangers by hooking them onto a Nage-shi (a type of horizontal shelf). I bought it on Amazon about a year ago, but it didn't fit, so I've kept it stored away. Below is the product description from when I purchased it: ■ Nage-shi Rail Clothes Drying Rack Hook Made in Tsubame-Sanjo Material: Iron (chrome-plated finish) Total Length: 165mm Height: 60mm Width: 15mm Weight: 70g Thickness: 3mm Load Capacity: 3kg ★ Can be installed on Nage-shi rails up to 10mm thick (If there is too much space when hanging the product, adjust with cushioning material or paper, etc.)