From Citizen Soldiers - The U.S. Army from the Normandy Beaches to the Bulge to the Surrender of Germany by Stephen E. Ambrose

Digging the hole was often arduous, sometimes exhausting. A typical position would be in or on the edge of a wood, which meant many roots, as most of the trees in Belgium were planted in rows, close together. During the second half of December, when the nighttime thermometer began to go down to near or below zero, the ground was frozen to the depth of a foot or more. Pickaxes were hard to come by on the front and even when available they weren't much help. Sometimes it took hours to chip away enough frozen earth to get to unfrozen ground. Men used grenades or satchel charges to blow away the frozen earth.

Often it was just impossible. On the night of December 18-19, near Echternach, Sgt. John Sweeney of the 10th Armored Division tried to dig in, "but the ground was made up of heavy wet clay and our entrenching shovel couldn't dig into it." After penetrating a few inches, he and his buddies gave up. "It was so cold that the rear echelon brought up some overcoats (2 for every 3 soldiers). We placed one overcoat on the ground and three of us lay on it and covered ourselves with the second overcoat. The only one who was warm was the middle guy so we changed places every twenty minutes or so. "

The holes were usually rectangular, under the best conditions four or five feet deep, two or three feet wide by six feet long. When the men were in them for more than one night, or if they were veterans, they got them covered.

Sgt. Leo Lick of the 1st Division, a veteran of Sicily (where he won a Silver Star) and the Normandy invasion, moved into the line near Butgenbach at twilight of December 17. He and two buddies worked on their hole for a week. They got some logs which "we put over the hole and then put branches over the logs and then covered that layer with soil and camouflaged the top with snow. We also put six inches of evergreen needles on the bottom of the hole for comfortable sleeping. The opening to the foxhole also served as a warfare trench from which we could shoot or stand guard." (Lick visited the site in 1986 and found the hole still there, an experience I've shared with a number of soldiers who were in the Bulge.)