What is a sgian achlais? It translates as “arm pit dagger”, and was worn concealed under the arm.
Where the sgian dubh was almost certainly a utility knife, the sgian achlais was truly a concealed weapon. How exactly it was concealed is not well documented — it’s up to you to figure it out for yourself. Probably slung with a leather strap or cord. Possibly just tucked into the folds of a great kilt, or inside a jacket. We have so many beautiful options you’ll have a hard time decide which one to buy first.
An alternative name sometimes seen for this weapon is “mattucashlass.” The meaning is the same, although the name was derived from a different dialect of Scots Gaelic.