Thornberry is an imposing but technically gifted central defender who came through the Ilkeston FC academy.
Joint manager Paul Donnelly says that Thornberry is a player that will serve Belper well in the long term.
Donnelly said: ”He’s got a lot of ability on the ball, he may not be one that is in the team week in week out but he will certainly have the chance to prove himself and take his opportunity.”
The Nailers have also added forward Dexter Atkinson, who was also previously with Ilkeston FC before they dissolved.
Atkinson offers the Nailers a number of options, with his ability to play as a central striker as well as playing as one of the wide men.
The 21-year old has previously played for Europa Point FC in Gibraltar as well as Dunkirk, Stapleford, Clipstone and Sheffield FC.
Donnelly believes that Atkinson has the potential to be one of the fans favorites this season thanks to the ability that he offers.
Donnelly said: “I think the fans are really going to like Dexter, he is extremely quicky, he’s got good feet and he’s a very positive player.
“I’m sure that there are things to work on with him, but he’s the sort of player we want to bring into the club. He’s young and he’s hungry so we think Dexter is one that will excite the fans.”
Updated 23:49 - 18 Jul 2017 by Dominic Hynes