A gridiron is a metal lattice for broiling or grilling food (or, in the case of St. Lawrence, saints). It’s a period charge, found in the canting arms of the Worshipful Company of Girdlers, 1454 [Bromley & Child 109]. The gridiron is palewise, handle to base, by default.
There is also the “spiral iron”, likewise used for grilling food. Though a period artifact, dating from the Iron Age in Scandinavia, it’s not been found in period armory. The spiral iron is palewise, handle to base, by default. See also frying pan, portcullis, strike.
Maren Lauritsdatter bears: Per pale azure and vert, three gridirons argent.
Domenico Barbiere da Mantova bears as a badge: A gridiron sable.
Brian fitz Gerald bears as a badge: Argent, a spiral iron sable, a bordure gules.