Source: https://guthlabs.ai/docs/instruments/fence-materials-calculator/implementation/

instrument implementation / implementation-contract

# Fence Materials Calculator implementation

A source-bound implementation contract for Fence Materials Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t4-067

**Effect**: Computation or source lookup only

## Input and validation requirements

Zero post spacing or zero picket width-plus-gap produces undefined divisions, so the calculator must reject those inputs. The specification also lacks a formula for rail/concrete estimates and does not define how gate_count affects material counts.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "total_length": 120,
    "post_spacing": 8,
    "picket_width_spacing": 0.5,
    "length_unit": "ft",
    "gate_count": 1
  },
  "expected_outputs": {
    "post_count": 16,
    "picket_count": 240
  },
  "working": "Posts: 120 / 8 = 15; ceil(15) = 15; 15 + 1 = 16. Pickets: 120 / 0.5 = 240; ceil(240) = 240. gate_count is not used by the supplied formulas."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/fence-materials-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/fence-materials-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/fence-materials-calculator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche4/tranche4-results.json`