Garden

[tezestwing]

what do scarifies do and what size do they come

[Old_Geezer]

I find that they have a tendency to rip up all and sundry. The moss removal is good, the lawn/mud removal less so.

[Chipchopper]

You can scarify a lawn with a spring bock / wire rake by briskly raking towards you and scraping out (thatch or thub) and also moss dead grass etc, which can prevent the lawn from draining freely.

On a more industrial scale, for larger areas you can buy or hire a petrol driven machine which will save you all the donkey-work but may hard on your pocket, so depends on your budget and size of lawn really.

[Ryzen]

Use a moss killer if required and a few days later use a scarifier on a gentle setting, then collect the moss/thatch ,etc. Let the grass recover for a week,cut it then scarify again until all the thatch is out. Dont try to do it in one go or you may end up with lots of bare patches.