Grays Athletic chairman and caretaker-manager Mike Woodward has made former Millwall defender Ronnie Bull his first signing for the Blues. Bull has signed a contract until the end of the year but with the option of an extension.
The 25-year-old left-back was a free agent after leaving Rushden and Diamonds in the summer.
Bull also played for Grimsby Town and had loan spells at Yeovil and Brentford after starting his career at Millwall.