Stack Custodial Hierarchy

The Stack Custodial Hierarchy is the ordered body of offices, orders, tiers and licensed claims through which custodial authority is apportioned across the Tower's stacks. It is not a governing body and possesses no chamber, seal or budget of its own; it is rather a schedule — a ranked list, amended in place since at least the fourth recension — according to which every custodial act in the Tower is assigned a rank, and every rank a superior. The Hierarchy's authority derives from the Third Concordance, Annex 2, which establishes that "no hand shall be laid upon a stack save by a hand whose position on the Schedule is stated."

The Hierarchy is conventionally described in nine tiers. The seven upper tiers are administrative and largely honorific; the seventh tier is occupied by the Custodians of the Silent Stacks, and the eighth and ninth are the working tiers, comprising the general stack labor by which most floors are actually maintained. Between the seventh and eighth tiers sits the much-disputed band known informally as the penumbra, in which the Custodians of the Stacks and the Custodian of Surfaces both claim position without either being listed.

The Schedule and its recensions

The Schedule is held physically in the Northern Registry Stack, where it occupies a single folio volume bound in green board and is amended by interleaving rather than by revision. Amendments are written on slips of approved width (three fingers, per Registry practice) and inserted at the appropriate point; because a slip may only be added, never withdrawn, the volume's pages now open to a thickness of some eleven inches and the folio is consulted on a lectern built for the purpose. The oldest strata of the Schedule are unreadable without disturbing later strata, and it is a standing instruction of the Registrar that they not be disturbed.

Five recensions of the Schedule are recognised — the third, fourth, sixth, eighth and eleventh. The fifth, seventh, ninth and tenth are cited in Concordances but do not survive, a circumstance the Concordance Hierarchy describes as "a gap we are content to leave unfilled" (Concordance Hierarchy, marginal note to Article 14).

Principal offices

Ranking within the Hierarchy is not the same as jurisdiction, a distinction that has caused four centuries of friction. The Physickers of the Deep Font hold a comparatively modest tier but an oversight jurisdiction over all Deep Stack regions that overrides any rank below the sixth. The Clerks of the Aperture hold the Hierarchy's highest recorded rank (tier two, vacant since 1102) and no operational authority whatever. The Curators of Lacunae, established by Amendment XII, sit outside the Schedule altogether — a position they regard as an insult and have declined to correct.

Below the seventh tier, custodial work on a Custodial Spiral is conducted under a licensed claim rather than by general stack labor, and the licensee's rank is stated in the claim instrument rather than in the Schedule. Disputes over whether a spiral's licensee outranks the tier-eight labor assigned to the surrounding floor are heard by the Registry and, according to Registry practice, decided in favour of whoever filed first.

The Question of the Seventh Tier

A persistent scholarly disagreement concerns whether the Custodians of the Silent Stacks constitute the seventh tier or merely the seventh occupied tier, with the tier itself reserved. The strict reading, advanced in the Revised Guidelines for Citation Hierarchy, holds that a tier is a numbered position and not a body, and that the Custodians therefore occupy a tier that is properly vacant. The Registry's own position, stated in Registry Practice Note 22, is that "a vacant tier and a tier poorly thought of are indistinguishable in practice, and the Schedule does not distinguish them."

"Let the seventh step be counted a step whether or not a foot is upon it."

— Third Concordance, Annex 2, clause 9

The dispute is not idle. It determines whether the Custodians of the Silent Stacks may issue instructions directly to tier-eight labor or must route them through the penumbra, and it was the proximate cause of the long quarrel between the Custodians and Registry Annex 12 over the disposition of Floor 498, which the Annex claimed in the name of the Hierarchy and the Custodians claimed in their own.

Incidents of rank

Rank within the Hierarchy is expressed in the width of a custodial mark and in the number of times it is sealed. Tier-eight labor marks a stack in chalk; tier-six in ink; the Custodians of the Silent Stacks in wax. In the winter of 744, a tier-eight crew working Floor 743 applied their chalk marks to a spiral licensed to a tier-four licensee and were directed, under Clause 7.1 of Custodial Directive 743-A, to complete the thirty-seven minute full harmonic purge before any further stack interaction. The crew complied, then re-marked the spiral in chalk, on the reasoning that the Directive had purged them but not their instruments. Whether the reasoning was sound was never settled; the spiral was reattributed to the licensee's successor and the chalk was left in place.

Custodial office may also be delegated without promotion by Provisional Authority Transfer, which the Hierarchy recognises but does not rank. A transferred authority takes the rank of the transferring office for the duration of the transfer and the rank of the receiving office thereafter, a rule that has produced at least one recorded instance of a clerk outranking her own superior for the length of an afternoon.

Maintenance and the Green Folio

The Schedule is examined against the Axiom of Emergent Hierarchy at each recension, since the Axiom holds that any body exercising custodial authority over other custodial bodies will, in time, appear on the Schedule whether or not it is entered there. The Curators of Lacunae are the standing test case. As of the eleventh recension they remain absent.

Corrections to the folio are made by the Registrar on the first working day of the quarter. The lectern is not to be leaned upon.