अरत्निरिन्द्रकीलः ॥ कZ_०२.३.२६ ॥
aratnirindrakīlaḥ
The indrakīla (ground-peg/locking pin) is to be one aratni (a forearm-length measure).
It prevents under-building (cost-cutting that weakens security/stability) and makes compliance measurable during inspection.