Landlords refusing to sell pints to women in pubs.
And ordering "a pint of bitter and a half of lager in a lady's glass" at the bar.
Half day closing was apparently enforced to help reduce the working week for those shop workers who invariably worked all day Saturdays. The reason all shops in a locality closed on the same afternoon was to make sure the shops that were open didn’t take trade away from those that were shut that day, initially shops were free to choose their own half day.
I remember a conversation as a child . . .
[Youthful me] "Dad, dad! Why are all the shops closed on Wednesday afternoon?"
[Dad] "Well son, the shopworkers need to work all day on Saturdays, so they have an afternoon off during the week to get their own shopping done."
. . . just to show that lame dad jokes are not a new thing.
As this is a Rail Forum, back in the steam era, one knock-on effect was some railway & bus timetables for more rural routes had mid-day local trains shown as WO and WX (maybe there were TuO & ThX variations too, depending on the location) to allow for half-day closing. The Ormskirk to Southport trains come to mind (half-day closing was Wednesday in Ormskirk). I suspect these variations died out in the 1950s or early 60s.