Pocket Knife with Kilt

[Jock Scot]

A mattucashlass is a type of dagger worn concealed in the armpit and primarily used for close combat, part of traditional Scottish male Highland dress. It is also referred to as an armpit dagger or a sleeve dagger in English. In Scots, the alternative name skene-ochil or skene-occles can also be found.

I must for the sake of clarity, point out that the sgian achlais(and other versions of spelling) the armpit Scottish dagger or sleeve dagger is not part of traditional Scottish kilt attire of today.

It certainly has historical connections to it, but a knife worn under the arm pit or up the sleeve would, in normal circumstances, most certainly be illegal these days in the UK including Scotland and no doubt I imagine, in many other parts of the world too.