Forward assist

Forward assisting is the practice of moving the bolt or bolt carrier of a firearm fully forward when the return spring has not done so (or there is a chance that it will not have done so). Some firearms have a dedicated device to allow forward assisting; on others, it is simply a procedure performed on the cocking handle.
As a device.
The forward assist on a firearm is a button found commonly on AR-15 rifle derivatives, such as the M16 rifle, and is usually located near the bolt closure. When hit, it pushes the bolt carrier forward, ensuring that the bolt is locked. In order to ensure that the extractor is clipped around the rim of the casing, the forward assist is usually struck rather than pushed. It is commonly incorporated into standard loading procedure to prepare a firearm for firing, or to close the bolt when the firearm is excessively dirty.
Another instance where the forward assist can prove useful is when performing a stealth chamber check. Rather than letting the bolt go forward under full spring tension after verifying a round is in the chamber, the bolt can be let forward gently and then the forward assist can be used to fully close the bolt. Doing so will produce a very distinct "click" rather than the loud sound of the bolt slamming forward. 
The forward assist had been implemented in 2007 on the MSAR STG-556, a U.S.-made clone of the Austrian Steyr AUG rifle, but the usefulness of such device is questionable, since the design is not normally prone to the malfunction that led to the need of the forward assist in other firearms; in fact "Microtech Small Arms Research Inc.", the manufacturer of the STG-556, has dropped the forward assist on all rifles manufactured since November 2008.
As a procedure.
On firearms where the cocking handle is permanently connected to the bolt or bolt carrier, a dedicated device is not necessary as the bolt can be assisted forwards by simply pushing or tapping the cocking handle forwards. 
The forward assist is generally not necessary as a standard procedure on any firearm with the exception of the British SA80. Having realized the frequency with which the firearm jammed when taken outside of the clean environment of the test range, the forward assist was implemented to save the operator the potential danger of aiming the rifle and pulling the trigger and the rifle not going off because the bolt is not fully forward (a safety arrangement called a "safety sear" stopping the hammer from being released and the firearm firing, because of the dangers of firing with the bolt not fully closed).
The design of the L85 makes the forward assist quite awkward as the left supporting arm must come off the hand grip and reach over the top to strike the bolt forward with the left edge of the left hand, much like a "karate chop". It may be a perception of awkwardness by external users due to unfamiliarity, as the drills are not seen as awkward by common users, it is a slick and swift drill when carried out by trained personnel where reload and ready times are similar to that of M4 type counterparts.
Further considerations of use.
The forward assist's use can correlate with an increase in malfunctions with feeding and extraction. Test data from the original trials indicate that, while the forward assist itself is not causal to inducing a malfunction, the need to use the forward assist will likely coincide with feeding and extraction issues exclusive from the use of the forward assist. While the forward assist can be effective in some circumstances as the tests demonstrated, the firearm's user should know when a to conduct a remedial action, such as cleaning the firearm, if repeated feeding and extraction issues present themselves and as time allows. It has also been demonstrated to be a safe mechanism to use even when held while firing.