A stitch weld is a sequence of short weld segments separated by gaps. The pattern is described as 'X mm weld at Y mm centres', for example 50@200, meaning a 50 mm weld every 200 mm along the joint.
Stitch welds reduce total weld metal (and therefore cost and heat input) on long joints where a continuous weld is overkill. They also reduce distortion: a continuous full-length weld pulls the parts together more aggressively than a stitched one.
For structural gate joints (mitre corners, hinge plates, drop-bolt receivers), full-perimeter continuous welds are standard. Stitch welds are common for non-critical attachment, batten brackets to stiffener bars, decorative trim to faces, anywhere visual quality and load capacity are both relaxed.