The slide-butt is a strong, oblong box, sufficiently capacious to hold three or four common wheel-barrows of earth or compost; it is shod with thing rough pieces of timber, and is convenient of spreading dressing over field, in small heaps. Two oxen, or one horse are employed to draw it.
Source: wiktionary
SLIDE-BUTT, in Agriculture, a sort of sledge in the form of a strong oblong box, shod underneath with thick pieces of timber. It is chiefly used for drawing manure from place to place, but chiefly in fields. It will contain about three wheel-barrows' full. Sometimes the butt has wheels, and when this is the case it is called a gurry.
Source: wiktionary