Skarz is expected to make his debut in Saturday's home clash against fellow promotion hopefuls Dagenham.
Simpson told the club's official website: "He is a recognised left-back and has played over 60 games at a higher level and will be a good addition to the squad.
"The thing that pleased with me with Joe is that he had options to go elsewhere, including a League One club, but he said no and jumped at the opportunity to come here.
"That is the enthusiasm and determination I want from players who want to come to this club and hopefully we will get some more."
Source: Team Talk
Source: Team Talk