What is the difference between locking a day and skipping a run?

These are two different ideas, and it helps to keep them apart.

Locking holds a day in place

Locking says "keep this day exactly as it is". The workout — or the rest day — standing on a locked day will not change when your plan next updates. Locking does not rebuild your plan.

Use locking when the day is already what you want, and you want it protected.

Skipping changes what the day holds

"I cannot run on this day" (skip) says "I am not running". TrainAsONE removes the planned run and the day becomes a rest day. Like locking, skipping does not rebuild your whole plan — it is a quick, local change to that one date.

Use skipping when you are not going to run. If instead you want to run but the plan has a rest day, use "Let TrainAsONE plan this day", which asks TrainAsONE to schedule a run (this one does trigger a plan update).

Which wins if both apply?

Your explicit day-by-day decision takes precedence over the automatic rolling lock. If you skip a run — or ask TrainAsONE to plan one — on a day inside a rolling lock, that day is respected for the next plan update, and the rolling lock itself is left untouched.

When these controls are not offered

Neither control is shown on every day:

• A race day offers neither — nor the padlock, nor the Training Day Rules pencil. The race owns the day, so edit or delete the race to change it. See How is a race day shown in my training plan?.
• A day whose run is already behind you — counted and analysed — offers neither either, because there is no longer anything to freeze or to skip.
• A post-race rest day keeps “Let TrainAsONE plan this day” (to return to training early) but not “I cannot run on this day”, since the day is already a rest day. See What is a post-race rest day and how do I change it?.