From Page 73 of the Carter book:
The large tents that had protected us so well during the winter from cold and rain were exchanged for shelter- tents [aka] "dog-tents," the boys called them. Everything was put in trim for an active campaign and a grand forward movement.
In active campaigning, the soldier carries his small tent (dog) and he and the comrade who is his "partner" put the two pieces together, which makes a comfortable protection from the weather.
His haversack contains his rations, while from his belt or saddle clatters a small coffee pot or pail, and in less than a half-hour after a halt the veteran knows how to prepare a wholesome meal of bacon, coffee and crackers, familiarly known as "hard-tack."
This new-fangled tent was very appropriately named by the boys, and was little better than no tent.