Rear Rack U-Plate Mount
Common models of bicycle rear rack in the market uses the seat pole mount to secure itself but some models do not have long enough arm to reach the seat pole mount. So instead it attach to a this u-plate adapter mount. Most bike will have an existing hole in the rear frame part where the vbrake is mounted at. Use that hole to mount this plate on, you can mount the rear vbrake together along with this u-plate.