There have been some statements made which I have overheard that need correction. The reason that these are being presented here are that they seem to be present in more than one situation by more than one person. There are three elements of the sword which are going to be discussed here, fullers, piercings and cross-guards or quillons. The reasons for these discussions will become clear as the discussions proceed.
1. The FullerThe fuller is a shallow channel which you will find present on some swords. It is most likely found on swords with a wide blade. It has been referred to some as a "blood groove" with the explanation that it allows the easy withdrawal of the sword when thrust into a person. It is not a "blood groove" at all.
The purpose of the fuller is to lighten the weapon while strengthening it at the same time. This feature of the blade is added during the construction of the blade. Attempting to add a fuller or fullers post-manufacture will weaken the blade, possibly in two ways. The first way is that by taking metal away from the blade it weakens it, and the second method is by heating the blade, especially by grinding or other modern methods, this can affect the temper of the blade.
Just as with the addition of a fuller or fullers, above, the post-manufacture addition of piercings to a blade will weaken the blade and shorten its potential life and for similar reasons to the addition of post-manufacture fullers. The removal of metal from the blade creates an inherent weakness in the blade, also the creation of any piercing by modern means will, again, create heat which can affect the temper of the blade around the area in which the piercings are made, thus creating weakness.
3. Cross-guard and QuillonsThe final discussion to be made is a matter of lexical accuracy when discussing weapons. People will randomly switch between the use of "cross-guard" and "quillons" for various weapons and with free abandon. What should be noted, and to be more accurate when discussing the terms, is that the term "cross-guard" should be used to refer to weapons up to the seventeenth-century, after which the term quillions should be used. This is especially the case with regard to single-handed weapons.
Interestingly, the term being Middle French in origin, was not picked up by the English until the 19th century (https://en.wikipedia.org/wiki/Crossguard) so should not be used at all when referring to English weapons at all until the 19th century.
These are three curatorial points which people should keep in mind when discussing swords, examining swords, and thinking of modifying their own weapons. Care needs to be taken so that a perfectly good weapon is not destroyed by a rash decision to make a sword "faster", where some more training and application will have much longer lasting effects. The modification of the sword to take a couple of grams off the sword will not effect the speed all that much, but may shorten the life of a sword considerably.