When you shrink heat shrink tubing, You use lots of heat sources like lighters and matches. Often this leaves nasty burnmarks on the tubing. But there's a very easy way to avoid this

Put the piece of tubing over the steelthread.









Put this in a heat resistant glass.








Boil some water and pore it in the glas, just enough to submerge the part with the tubing entirely.










Leave this for a minute. The heat shrink tubing will shrink automaticly from the heat of the water. And without the ungly burnmarks.