Interesting find at a Dahshur: while excavating near the 13th Dynasty Pyramid of King Emnikamaw, a burial chamber containing canopic jars of the King’s daughter were discovered. The above image indicates the use of an Isosceles Trapezoidal Prism Portcullis block let-in to a stone channel. Also of note are the dove-tailed slots cut to receive butterfly cramps used to join the stonework (see corner of right spanning block).
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Dr. Troglodyte