Make holes in the rockwool
How it's done
In case that your rockwool is combined with many pieces in one big piece now is the time to split it in those smaller blocks.
1. Take a small stick, wooden or plastic it doesn’t matter, just make sure that it is not more than 2.5mm wide. For example you can use stick for placing small meat pieces on the grill or toothpick.
2. From bottom of the stick measure 6 mm and with the marker or pen write a tin line exactly on 6mm point from the bottom of the stick
3. Take each block of the rockwool and push the stick in it so that you reach that 6mm mark that you’ve previously made. Please take special caution to make sure you don’t push the stick more than 6mm in the rockwool.