"Le jardinier porte des bottes épaisses."
Translation:The gardener is wearing thick boots.
I wrote "heavy" and got it wrong... But one translation of "heavy" into French is "épais." https://www.collinsdictionary.com/dictionary/english-french/heavy Maybe boots aren't considered "material" as the link shows. So I don't know!
I grew up in a farming and logging area. A common expression would be thick-soled boots. Otherwise, more generally, one would say heavy boots or sturdy boots. If an outsider were to use use the term thick boots, it would be readily understood, though considered a little odd. Perhaps this common usage elsewhere.