A rocket engine's turbopump is a precision mechanism, tolerating no contaminants to upset its fine tolerances; it also had to be protected from extremes of humidity. When not attached to an S-IC stage or test stand fittings, the F-1 turbopump's inlets were covered with closure assemblies.

Click image for a 1032x971 pixel version of this image in a new window.
Adapted from page 2-179 (page 7 of the PDF of section IIc) of the F-1 Rocket Engine Technical Manual: Illustrated Parts Breakdown.
Scan courtesy Dept. of Archives/Special Collections, M. Louis Salmon Library, University of Alabama in Huntsville.
Extraction, cleanup, and adaptation by heroicrelics.

As seen in the diagram above, there are two different types of closures for each of the fuel and the LOX inlets, and each are comprised of multiple components:

1	RK395-44032-011	CLOSURE ASSY, Fuel inlet (NO. 1 and NO. 2 fuel inlet)
1A	RK395-38006	PROTECTOR, Flange (NO. 1 and NO. 2 fuel inlet)
2	ST3950180RKL021	COVER ASSY, Protective, inlet closure, fuel and oxidizer (NO. 1 and NO. 2 fuel inlet)
2A	ST3950153RKL001	CLOSURE ASSY, Fuel inlet (NO. 1 and NO. 2 fuel inlet) (Contains captive fasteners
2B	ST3950180RKL011	COVER ASSY, Protective inlet closure, fuel and oxidizer (Turbopump oxidizer inlet)
2B	ST3950180RKL011	COVER ASSY, Protective inlet closure, fuel and oxidizer (Turbopump oxidizer inlet)
3	G4088	FIXTURE ASSY, Preload, turbopump shaft (Turbopump oxidizer inlet) (Installed with RK395-44034-021 closure only)
3A	RK395-44034-021	CLOSURE ASSY, Oxidizer inlet (Turbopump oxidizer inlet) (Installed with G4088 fixture)
3B	ST3950092RKL011	CUP ASSY, Rotor clamp, turbopump shipping
3C	ST3950180RKL001	COVER ASSY, Protective, inlet closure, fuel and oxidizer (Turbopump oxidizer inlet)
3D	ST3950154RKL001	CLOSURE ASSY, Oxidizer inlet (Turbopump oxidizer inlet) (Not installed with G4088 fixture) (Contains captive fasteners)
4	ST3950173RKL001	CUP ASSY, Closure, oxidizer inlet, turbopump (Turbopump oxidizer inlet) (NHA RK395-00024)

The RK395-44034-021 oxidizer inlet closure assembly (the more complex LOX inlet closure) and G4088 (detailed below) were installed during engine shipment. Any bumps or road vibrations during shipment could cause damage to the bearings and seals of the turbopump's single, large shaft. The G4088 fixture assembly centered and loaded the shaft to keep it centered to smooth out any bumps or road vibration impacts on turbopump bearings and seals. The separate closure used with the G4088 was more complex to interface with the G4088.

See also G4088 installation instructions.

Click image for a 4294x3605 pixel version of this image in a new window.
From page 1-8 of the F-1 Rocket Engine Technical Manual: Transportation R-3896-9, excerpts of which are located in the Young collection of the Dept. of Archives/Special Collections, M. Louis Salmon Library, University of Alabama in Huntsville.
Scan and cleanup by heroicrelics.

See my photos of the ST3950180RKL001 LOX inlet closure in the Mark Wells collection and my photos of the RK395-44034-021 oxidizer inlet closure assembly on the F-1 rocket engine at the U.S. Space and Rocket Center.

Thanks to Vince Wheelock for his explanation of the two types of LOX inlet closures.