Many spades have a kind of lip on the top of the blade so that when pressure is applied ordinary footwear is adequate to protect the digger from pain.
Some spades, though, have quite a sharp top to them and tough soles are needed on boots or shoes.
Or alternatively, you could attach a digging plate to your boot or shoe. This consists of a sturdy metal plate and a leather strap to fasten it under the sole of a shoe.
A digging plate at Market Lavington Museum
This dates from late in the nineteenth century and was used by a man who had an allotment on Northbrook.
From the underside we can see that the plate had a little lip to make sure it didn’t slide off the spade.
The lip on the underside
Now there’s a real reminder of past times.
Market Lavington Museum 