A weld made to hold the parts of a weldment in proper alignment until the final welds are made.
A tack weld is a short weld made at intermittent points to hold abutting edges together. The length of the weld, spacing between welds, and design of the tack weld should always be specified. Specifications usually include the length of each tack weld and the measurement from center to center of the tack welds. The particular design of the tack weld is often not specified.