Paul Gendrop describes then east facade of the Labna arch as possessing "great sobriety...the principal motif is large stepped frets that stand out in strong relief over a background of colonnettes strongly underlined by the projection of the moldings."
Paul Gendrop, Rio Bec, Chenes and Puuc Styles in Maya Architecture, p. 190.
The two stepped frets which meet in a "V" in this detail on the east side of the Labna Arch suggest an extremely stylized mask to George Andrews, author of Pyramids & Palaces, Monsters & Masks: The Golden Age of Maya Architecture.
Labna Arch: east side showing damaged portions of the connecting building
In this photograph it is easy to see how Puuc construction techniques utilizing interior rubble fill surfaced with well cut plain and mosaic stonework was used to build the Labna arch. These are very solid buildings.