Abstract: The invention provide an improved trailer dolly and an improved trailer dolly tongue support jack. More specifically, the invention provides a trailer dolly which includes a tongue support jack which is effective and convenient to operate. In the preferred embodiment, the improved dolly includes a tongue support assembly permits the dolly tongue jack to be rotated between and automatically locked in the tongue support positions and the trailer use positions. Although the tongue jack was developed primarily for use with trailer dollys it can be used to support conventional trailer tongues and similar uses.