The theory about how to harden off tender plants goes something like this:
Spend at least a week bringing them outside in the morning and indoors again at night. (Keep an eye on the weather forecast and plan this in advance when it looks as though you’re in for a warm, settled patch.) Accustom them gradually to the outdoors before planting them out in a carefully prepared sheltered spot.
The alternative goes something like this:
Realise your courgette plants are suddenly enormous and in danger of flowering in their too-small pots.
Drag them outside at whatever point in the day you remember to do so, whatever the weather. (Even the most imperfect gardener might avoid a frosty day, if only to protect her own fingers.)
Forget to bring them in at night because you were doing something else indoors. (Possibly something involving feeding or otherwise dealing with family members who, unlike plants, have the ability to complain if neglected for too long.)
Reason that, if they have survived one night, another can’t possibly hurt them too much.
Plant them into a patch of ground from which you have removed most of the weeds, roughly guessing a) how far apart courgette plants are supposed to be planted and b) how many of your hand-spans that equates to, because looking things up in books and finding a ruler will take far too long and smacks of super-organisation.
Cross fingers and hope for the best, popping a few courgette seeds directly into the ground as an insurance policy.
Convince yourself you can’t be a really terrible gardener if your broad beans are flowering so well, and comfort yourself with a snack of some homegrown radishes.