>>347935They have 4 total generally and they work like caltrops, there is always at least one pointing directly up and I've felt them regularly even through thongs(flip flops, not sure what you call them in America?) They're quite robust and take a bit of force to remove, basically they're my number one pet hate when /out/ because they're completely pervasive.
Apparently the proper name is Spiny Emex and "doublegee" is a bastardisation of Afrikaans.