Sides (in modern times often called "Siding") is a dance step used in English Country Dance. Although The English Dancing-Master makes no specific description of the step, from the choreography it can be established that it is always performed by two people together, and that its duration is that of two doubles. The version that seems to be usually accepted as the best guess as to what figure Playford intended comes from Recueil de contredances by Raoul-Auger Feuillet. This version was explicity shown in diagrams, which indicated each dancer's starting place, facing, and path across the floor, and the timing of the figure.
It is done by two dancers facing (by default this is assumed to mean partners, if no other pairing is specified). They go forward in four counts, on a diagonal slightly to the left, to meet with right side by right side ("sides by the right"), then fall back to their starting places in four counts. The second time, they go forward to the opposite side to meet with left side by left side ("sides by the left").
There are many variations on this figure, including doing the above but meeting by the left side first, Sharp siding, and even a double-time version done in Lochac.