The SIGHT is held to the BED by a Cross-pin which traverses both the Bed and the Sight Leaf itself and forms the axis around which the Sight Leaf rotates. They are held in place by a smaller Cross-pin which passes through the end of the main Cross Pin (the axis pin). There is also a Washer there to keep everything solid; it is grooved for passage of the small Pin.
The BED has on it a Spring which is screwed in place and provides pressure to the Sight Leaf. This Screw can be removed without disassembling the Sight.
The BED is held to the Barrel of the Rifle by a Cross-pin passing through the Rear Sight Bed and GRAZING the Barrel. Putting this pin in is the hardest part. By removing the Spring Screw, you can sight directly down through the Sight Bed to the Barrel itself. There, you will see a mark where the Screw strikes the Barrel.
By lining up this Screw perfectly, you will also put the Bed in the correct position for inserting the Pin to hold the Bed to the Barrel. You then tap the Pin into position.
That's all there is to it.
That's for the SMLE Mark III and III*. On the older model, the Mark I which was made only from 1901 through to 1907, the Rear Sight Bed actually screws directly to the Barrel and is soldered in place.
Hope this helps.
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