The nomadic midfielder, who has played for no less than 13 clubs prior to joining the Valiants, signed a short-term contract until December 28 earlier this week.
The deal was not ratified in time for Jarrett to feature in the 2-2 draw against Accrington on Tuesday but the 30-year-old may start this weekend, with Doug Loft the most likely to miss out.
Jarrett told the Sentinel: “I was a little bit behind in terms of fitness a few weeks ago, but I’m really keen to make my mark and then see how it goes.”
Although his side have now gone four league games without a win, manager Micky Adams is unlikely to make many more changes to his starting line-up.
Joe Anyon is closing in on full fitness following six months on the sidelines with a broken leg, but the goalkeeper is unlikely to displace young shot-stopper Chris Martin just yet.
Meanwhile, centre-half Luke Prosser has returned from a loan spell at Blue Square Premier side Salisbury.