The man first measured the thickness and the height of the wall around the temple complex. Measuring not only provides data but implies ownership (cf. Zech. 2:1; Rev. 11:1; 21:15); the man measured as God's representative. He used the six-cubit reed that was in his hand. The wall was six cubits (one rod) thick and six cubits high. Walls, of course, provided a barrier and guarded the holiness of God in Israel's earlier tabernacle and temple complexes.
A normal cubit was the distance between the tip of a person's middle finger and the end of his elbow, about 18 inches (Deut. 3:11). A handbreadth was about three inches. A long cubit was about 21 inches long, the length of a normal cubit plus a handbreadth. Since each of the cubits of the man's measuring rod was a cubit and a handbreadth, it seems that the cubits in view in these dimensions were long cubits (cf. 43:13). Six long cubits (one rod) equals about 10 feet.