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Problem Solving & Quality · Sustain

Horizontal Deployment (Yokoten)

Copy the proven countermeasure to every similar machine, line, product or site where the same cause could strike — and check it was applied.

  • Time45 min
  • FormatSmall group
  • StageSustain

Horizontal Deployment (Yokoten): what it is and why it works

Yokoten, often translated as horizontal deployment, is the practice of spreading a proven countermeasure to every similar place where the same cause could occur: identical or similar machines, other lines, other products, other sites, suppliers or future projects. It starts by describing the cause and the fix in terms another team can recognize, such as equipment type, material, design feature or practice, rather than the local details of the incident. The owners of each potentially affected location then assess and apply the fix, or explain why it does not apply, and a sample is checked on site.

The same failure often hits a sister line or another plant months after it was fixed at the first one, because the knowledge stayed where the problem occurred. Yokoten turns one team's problem-solving effort into protection for the whole organization, often at a fraction of the original cost. In the Toyota tradition, it works best as peer learning: teams invite each other to see the countermeasure where it was made and adapt it, rather than receiving an order. It is the D7 discipline of an 8D in practice, feeds the lessons learned register and often spreads poka-yoke devices from one line to all similar lines.

What you need

  • A verified root cause and a countermeasure proven effective
  • A description of the cause in generic, recognizable terms
  • An inventory of equipment, products and sites with similar features
  • Named owners for each potentially affected location

What you get

  • A deployment sheet sent to each affected owner
  • A status list: applied, not applicable with reason, planned with date
  • Audit results confirming the countermeasure is in place
  • Inputs to design standards and the lessons learned register

When to use it

When the same failure hits the sister line six months after it was fixed on the first one.

How to do it, step by step

  1. Describe the verified cause and the countermeasure in terms another site can recognize: equipment type, material, design feature, practice.
  2. List where the same cause could exist: identical or similar machines, products, sites, suppliers, projects.
  3. Send a short deployment sheet to each owner, with a deadline to assess and apply.
  4. Collect the answers: applied, not applicable with reason, or planned with date.
  5. Audit a sample on site to confirm the countermeasure is really in place.

Worked example: Gearbox failures on identical extrusion lines

Illustrative scenario — figures are realistic but not from a real company.

A building-products company runs four plants with a total of eleven identical profile extrusion lines. At one plant, a main extruder gearbox failed after less than two years, causing nine days of downtime. The root cause was an oil of the wrong viscosity grade, introduced when a local purchasing change consolidated lubricants. The plant fixed it by returning to the specified oil and labeling fill points with the oil grade.

  1. The reliability engineer described the cause in generic terms: "gearbox oil substituted with a different grade during lubricant consolidation, without engineering review". The countermeasure was the correct oil, labeled fill points and a rule that lubricant changes need engineering approval.
  2. The inventory listed the 10 other extruder gearboxes, plus 14 downstream haul-off and cutter gearboxes that used the same lubricant list.
  3. A one-page deployment sheet with photos went to each plant's maintenance manager, with 30 days to check the oil in service, apply labels and confirm.
  4. Answers came back: three plants found no issue, and one plant found the same substitution on two extruders and one haul-off, where oil analysis already showed increased wear metals.

Result. The affected gearboxes were drained, flushed and refilled, and their oil analysis returned to normal over the following months. The engineering approval rule for lubricant changes was added to the company's maintenance standards. An on-site check at two plants confirmed the labels were in place. The cost of the deployment was a few days of work, compared with nine days of downtime for the original failure.

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Common pitfalls and how to avoid them

  • Describing the fix in local terms, such as a tag number, that other sites cannot map to their equipment.Describe the cause and fix in terms of equipment type, material, design feature or practice, with photos.
  • Sending the information by email and assuming it was applied.Request a response from each owner, track status and verify a sample on site.
  • Limiting deployment to identical equipment.Also consider similar designs, other products, suppliers and future projects where the same cause could occur.
  • Imposing the fix without explanation, which triggers resistance.Share the story and evidence, and invite peers to see the countermeasure where it was implemented.

Frequently asked questions

What does yokoten mean?

Yokoten is a Japanese term often translated as horizontal deployment or sideways expansion. In Toyota practice, it refers to spreading learning, such as a countermeasure or a good practice, across similar processes, lines and sites. The emphasis is on peers seeing and adapting what worked elsewhere, rather than simply copying it.

How is yokoten different from lessons learned?

Lessons learned captures knowledge in a record so it can be found and reused, often for future projects. Yokoten actively pushes a proven countermeasure to existing places where the same cause could occur now, and checks that it has been applied. The two complement each other: yokoten protects current operations quickly, while the lessons learned register preserves the knowledge for the future.

Who is responsible for horizontal deployment?

The team that solved the problem is usually responsible for describing the cause and countermeasure and identifying where else it could apply. The owners of each affected machine, line or site are responsible for assessing and applying it. A central function, such as engineering or quality, often tracks the status and audits a sample to confirm implementation.

Origin

Yokoten (horizontal deployment) — Toyota practice; no single author.

Used in these playbooks

Customer complaint closure 4 weeks

Four weeks to answer a complaint the way customers expect: a structured 8D, a clean problem statement, causes of occurrence and escape, an error-proof fix and deployment to sister lines.

  1. 8D Method
  2. Deviation Statement
  3. Three-Path Whys
  4. Poka-Yoke
  5. Horizontal Deployment (Yokoten)

Related methods

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