defender TD5 air box clean

[mattmac]

Was just changing air filter and noticed inside airbox a bit dusty so decided to remove completely to clean- pulled out rubber bung and quite a bit of dirt/crude fell out - gave it good clean but also noticed there is a small square hole in bottom(presumably from factory) of airbox and wondering what it's for-seems strange as would assume would want it to be completely sealed?

[trout1105]

I am pretty sure that the square hole is there as a drain hole to let water out.
If you have a snorkel fitted then most of us block that hole up to prevent water ingress.