Whilst I was serving in the RNR I was taught, as every other sailor was, how to use an SA80 rifle. Part of that instruction included fitting the rifle’s sling, a task that I must confess I always struggled with. The SA80 sling is incredibly versatile and a fantastic piece of kit to use, however it can be difficult to fit if you are not careful. My thanks go to Martin Johnson for kindly letting me have tonight’s sling. The sling itself is made from woven nylon webbing and is usually stored rolled up when not on a gun:
From the official SA80 manual, the description of the sling reads:
The sling consists of two lengths of webbing type material. The longer piece has at one end a female part of a clip and a flat plastic loop attached, the other end of the strap is clear. The shorter piece has the male part of the clip at one end and the quick release buckle and loop at the other. 
Here we can see the clip and in this instance a metal loop at the centre of the sling:
Originally this loop was plastic but it broke so frequently that it was upgraded to metal pretty quickly. The end of the shorter piece has a loop and a friction buckle:
The designation of the sling and a year of manufacture are printed onto the sling in white lettering:
Fitting the sling is also described in the manual:
Join the sling together using the male/female clip ensuring the that flat loop and the ridged edge of the gate are the same way up.
Take the longer strap and lay it flat along the weapon with the female clip end towards the muzzle and the flat plastic loop pointing outwards. Feed the clear end through the front sling loop and then through the flat plastic loop on the strap and over the ridged edge of the gate in the base of the male clip and pull tight (Stage 1 and 2).
Ensure that the longer strap remains untwisted and then feed the clear end through the rear sling loop on the weapon (Stage 3).
Check that the shorter strap is not twisted and then feed the clear end of the longer strap outwards through the main gate of the buckle bar. Finally, thread the clear end of the longer strap back through the gate in the buckle (Stage 4).
Once completed the rifle and sling should look like this:
This sling allows the rifle to be carried in a number of different ways, including slung over the back in a rucksack style when both hands need to be free such as when skiing:
Tales from the Supply Depot 
Fitting the sling correctly was indeed tricky. To make training easier a “how to” video was issued which ran for about 20 minutes if I remember correctly!
Never had to sit through that one. I remember watching a very ancient one on the SA80 that was made when the A1 was introduced that had very detailed animations of how the sears worked- even for someone like me who likes weapons and understanding how they work found that one heavy going’