Cuttings and remains of dead plants cause thatch in the lawn, which can develop to a few centimetres in thickness. The result: Air exchange, the supply of water and fertiliser are handicapped or hindered. The lawn suffers! You can clear the air for the lawn by verticutting it. 
 The principle is obvious: If thatch has developed to the extent that it is detrimental to lawn growth, or even hinders it completely, then it must be scarified and removed. Thatch is insidious: Water, air and nutrients are held back from the lawn grass roots. As a result of the reduced air exchange, moss and deleterious fungal growth have the best environment for growth and threaten the weakened lawn grasses. Furthermore, the grass roots tend not to penetrate the centimetre thick thatch and develop laterally. In this manner, the root development is only superficial and unlikely to withstand periods of heat or drought. The lawn dies of thirst, because its roots are unable to extract moisture from the lower soil strata. 
 Lawn thatch can easily be removed with the verticutor. This process, by the way, was developed by WOLF Garden. As a matter of principle, the lawn should be verticut at least once per year. Normally the thatch should be removed from the lawn in March/ April. You'll be amazed at the amount of rubbish which results! In August/September, strongly invasive, flat growing summer weeds such as speedwell 

(Veronica) can be removed by a further treatment. Even if the lawn appears to be a little battered after having been verticut, there is no cause for concern. Helped along with fertiliser, small gaps close up quickly and larger gaps are re-seeded. All verticutters, whether power-driven or manually operated, are equipped with sharp blades which are either pulled or pushes across the lawn surface. Take care to ensure that the blades lightly touch the soil, but do not cut it open. 

Manual verticutters necessitate some practice and strength. Power-driven models are much simpler to operate. Whichever is used, it is im-portant to remove just the thatch  there is no call for re-working the surface of the soil. Verticutting too deeply damages the grass roots, damages the verticutter blades and causes excessive wear to the motor. For verticutting, the lawn surface and upper soil layer is dry.

 The whole surface should be worked track by track in the same direction, without leaving any gaps. After verticutting, the lawn is fertilised with  "Super" fertiliser.  

REF:Wolf Petrol Scarifier  

     
  REF:Wolf Hand Scarifier