A Mechanical trading system is a maintained procedure, not only an entry trigger

Specify the Mechanical trading system as one procedure

A Mechanical trading system is specified as a setup-plus-trigger sequence. Exit and abstention are treated as part of the same rule set rather than as optional afterthoughts.

The two-stage form is a setup-trigger: market conditions must be present before an automatic trigger can fire.

Inspect the procedure on a calendar

A Mechanical trading system is inspected on a regular schedule whether recent results are favorable or not. That inspection is a scheduled-checkup: a calendar review of a mechanical procedure in both favorable and unfavorable periods.

Waiting until capital has already been reduced is described as the usual but inadequate practice. Maintenance review includes taken trades, missed signals, shrinking winning-trade size, and whether the procedure still performs its designed function, such as capturing trends.

Read trend strength before a countertrend stance

Average Directional Index is used as a quantitative reading of trend strength. Ordinary directional movement can then be distinguished from a strong trend before a countertrend stance is taken.

Keep the same rule with a volatility-unit

Average true range is substituted for fixed dollar or point amounts so that breakout distance and profit units expand and contract with current volatility. The substitute is a volatility-unit: a range-based distance used in place of a fixed dollar or point amount.

Expressing a breakout as two average true ranges is presented as a way to keep the same rule aligned with a quieter or faster market without rewriting the formula.

ATR position sizing then treats position size and remaining capital as constraints that must bound a trade before entry. Oversized exposure on an anticipated event can force exits before the expected information arrives.

Override for catastrophic risk, not for disagreement

A mechanical signal may be overridden when catastrophic risk appears excessive, but not merely because the operator disagrees with the system's direction forecast.

Build multiple systems when one no longer matches

When a single trend-following procedure no longer matched a less trendy market, the documented design response was to build multiple systems rather than keep relying on one method.