Four compartments above, one below

The bayit shel rosh, the head-box, is built as four separate compartments — four channels of leather drawn up from one base and pressed together into a cube, each holding its own small scroll with one of the four passages on it. The bayit shel yad, the arm-box, is one compartment, holding one scroll with all four passages written out on it in sequence.

Same four texts. Divided above, single below.

Which is the reading the tradition itself makes of it, and it needs no mysticism to be striking: the head takes things apart and the heart does not. Above, four things held separately, side by side, distinguishable — which is what thinking is. Below, against the arm, opposite the heart, the same four run together on one strip as a single thing you either do or do not do. The object states the difference between understanding something and being moved by it, in leather, and it states it as a manufacturing tolerance.

⚠⚠ And this is where a claim this app very nearly made falls over, so it is recorded rather than quietly dropped. The obvious move is to read the boxes as three above and seven below — the three upper sefirot on the head and the seven lower on the arm, matching the Sefer Yetzirah's three mothers and seven doubles. It is neat, it is repeated widely, and the object does not say it. Count them: there are four compartments up there. The three-and-seven in tefillin is real but it is somewhere else entirely — it is in the strap, seven turns on the forearm and three on the finger — and the sefirotic reading of head-against-arm is eighteenth-century. Four-and-one is the object. Seven-and-three is the strap. Three-above-seven-below is a later gloss and is dated as one in tef-mochin. The overreach here was this app's own, caught while building the room, and left on the page because a correction you hide teaches nothing.