[...] there is no identified archaeological evidence: nothing that can show us exactly how long or heavy a lancegay was, what the diameter of the shaft was, what shape of head it had, or whether it had heads at both ends, as is sometimes claimed. There is also no detailed description of a lancegay in any known written source; and there is no instance in any of the visual media that can indubitably be identified as a representation of the weapon. As is so often the case with weapons terms in the Middle Ages, writers of literature and other documentary sources assume that one knows what technical words denote, making it unnecessary for them to supply explanations or descriptions. As a result, everything we believe we know about the lancegay has to be deduced from what is said about it.

-David Scott-Macnab, Sir John Fastolf and the Diverse Affinities of the Medieval Lancegay

There are no surviving fectbuch or manual involving a section on the lancegay, although there are surviving treatises (or sections thereof) on spears and lances, such as Fiori de'i Liberi, and the techniques involved would presumably have been similar.