Article below is a part of the assembly process of the UHF duplexer – main article is HERE.
Drawing below shows a [AL100] – 8mm Aluminium End Cap Top.
Main purpose of the part is to protect everything what is inside of the duplexer’s cavity and also to support a copper plate together with a copper conductor – the main resonance element. Unless you have a CNC router (or special skills :P) and you can drill all holes perfectly aligned, the best idea is to prepare [AL100] – 8mm Aluminium End Cap Top and [AL100] – Copper Plate together, so all the holes will perfectly align. I used a printed 1:1 drawings to pre-punch holes and then drill them on a pillar drill.