I know some parts on Caretaker's Catalogue say "Less Thak" or "Thak". This is not a common knowledge term so we are going to let you in on some industry lingo here.
THAK = Test Housing Assembly Kit
This virtually means everything but the valve when referring to the Caretaker parts.
Parts that include the THAK assembly are 5-9-2000
The THAK items include:
1 Bottom Plate(1-9-215)
1 Oring Kit(5-13-1)
1 Pressure Relief Valve(1-1-220)