Function of a windowed piston in a reed crankcase?

[Mr. Marmot]

Hi All. Since the intake flow from a reed crankcase always comes from underneath the piston, why do people use pistons with windows and/or cut skirts?
I can understand these pistons in "bolt on" reeds for extending the intake timing, but why do "true" reed crankcases benefit from them?
Thanks

 

[Dunc2504]

From what I gather it acts as another transfer port as there is a port in the cylinder wall like a wide groove from crankcase lip to the cylinder.

 

[HXRC]

Correct Dunc2504, it's called a "boost" port and it acts as another transfer port.
There's also "desert" ports which are typically used for piston cooling.