You can get stitches embroidered into robes. You can use the stitches for various things like increasing spell damage, spell haste, spell penetration, countering penalties to casting, and banding spell damage.
The maximum embroidery can give a bonus is (current skill in tailoring - 4). So, if you have a skill of 5, then you can create 1 point embroideries. You don't have to have the skill yourself.
When you use the stitch, it unravels. Obviously, if you have the skill, you can sew it back on, but you have to sacrifice the power again.
The ratio of banding spell damage is 1:2. In other words, for every 2 points sacrificed into the embroidery, you can band 1 point of spell damage. For the others, it's 1:1.
The embroideries must be visible although not necessarily detectable (e.g. when blended or sneaking). Even getting them dirty stops them from working until you have given the robe a good wash. Covering them with anything also stops them from working. They are obvious, although it is not necessarily obvious what they do.
You can wear armour underneath them, if it is leather. However, you have to subtract the wound conversion category of the armour from the force of all of the embroideries. You cannot wear metal armour underneath a robe. You'd look like a complete dick. You'd look stupid enough walking around with leather armour under your robes.