If you alter a piece of treated timber e.g. cut it to size or drill holes you are altering the treatment envelope which can make the timber once again susceptible to hazard attack particularly decay.
For all outdoor treated timber, all cut-ends, notches and rebates must be resealed with a suitable resealing product such as Tanalised® Ecoseal or Tanalised® Enseal Clear. This will ensure the treatment envelope is maintained for durability against termite and fungal attack.
With H4 treated timber, you should avoid placing a resealed cut-end or notched out surface in the ground.
For Timberlink Blue, resealing on cut ends, holes and notches is not required if used within the termite treated enclosed frame.