The pair featured in both of the Iron's pre-season games in the Republic of Ireland, though they were left out of the Lincolnshire Senior Cup loss to Grimsby. The club were required to sign players on non-contract terms in order to be eligible for that game.
"We had a look at the two of them when we were over there [in Ireland], since then we have been trying to do something with them," Knill told the Iron's official website.
Keegan, who previously spent time on trial at Southampton, spent last season playing for Monaghan United in the Irish league.