Mortise-and-tenon beam joints (trave a incastro)
Interlocking timber joints measured in braccia, with a tenon formed on two bases, and a weight device.
The upper margin shows a mortised beam ('trave a incastro') divided into equal segments each measured at four braccia, with an analogous figure of five such segments. A block is drawn 'prepared for the joint', its tenon — the tooth a n — formed on two bases, q n p and o a r, which Leonardo calls its utmost perfection. Several blocks with dovetail-like slots study how the timbers interlock, and a weight-driven device with a suspended ball appears at the upper left.
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Mortised beam divided in four-braccia segments
A beam built as an interlocking (mortised) member is drawn along the upper margin, divided into equal bays each labelled four braccia. An analogous figure repeats the arrangement with five segments of four braccia each.
Block prepared for the joint: tenon on two bases
A block is shown prepared for the interlocking joint, labelled r a o – p n q. The tenon (the tooth a n) is formed on two bases, namely q n p and o a r, and this Leonardo calls its utmost perfection.
Weight-driven device with suspended ball
At the upper left a framed device carries a ball hanging on a line above a boxed mechanism. No transcription accompanies it, so it is noted here from the drawing alone.