The following are excerpts from "Mediaeval Sinhalese Art"
There are several topics touched on here:

Craftsmanship.
"The simplest are of plain steel, but very graceful form, with wooden or horn handles, and carried in the belt by every villager, to lop off inconvenient branches as he passes through the jungle, to open coconuts, or cut jungle ropes. From these knives there are all transitions to the most elaborate and costly of silver or gold inlaid and overlaid knives worn by the greatest chiefs as a part of the costume, and never intended for use. The workmanship of many of these is most exquisite, the mounting and sheaths being equally beautiful; but this fine work is done rather by the higher craftsmen, the silversmiths and ivory carvers, than by the mere blacksmith. Many of the best knives were doubtless made in the Four Workshops, the blades being supplied to the silversmith by the blacksmiths."
Note: This book refers to these knives simply as "pihiyas".

Artistic Design.
Liya vela:  a term cited in both Mediaeval Sinhalese Art and a Catalogue of Antiquities to describe a commonly used design technique in Sinhalese art, and often seen on pihiyas. Liya denotes graceful, a vela is a climbing plant or jungle rope.

"In Sinhalese ornament liya vela has the technical meaning of vegetable ornament, consisting not of single flowers or leaves, but of a continous stem with rhythmically disposed floral or foliar elements."

example of liya vela

The Four Workshops.
"The best of the higher craftsmen (gold and silversmiths, painters, and ivory carvers, etc.) working immediately for the king formed a close, largely hereditary, corporation of craftsmen called the Pattal-hatara (Four Workshops); these men worked only for the King, unless by his express permission (though, of course, their sons or pupils might do otherwise); they were liable to be continually engaged in Kandy, while the Kottal-badda men were divided into relays, serving by turns in Kandy for periods of two months. The Kottal-badda men in each district were under a foreman (mul-acariya) belonging to the Pattal-hatara. Four other foremen, one from each pattala, were in constant attendance at the palace."