Broken screen hinge fix

Technically the is called the Clutch Cover it covers the hinge clutches which offers the tension to hold the display, in addition it covers the WiFI and Bluetooth antennas.

Here’s the part Display Clutch Cover you’ll need to take the display assembly off so you can slide off the old unit and slide on the new one MacBook Pro 15" Retina Display Mid 2012 Display Assembly Replacement basically you slide longitudinally just a bit so the catches clear then you put straight down, It’s about 6mm of shift needed

While one can pry off the old part you run the risk of damaging the antennas just underneath.