Clearance
Post boxes are emptied ("cleared") at times usually listed on the box in a TOC, Times of Collection, plate affixed to the box. In metropolitan areas, this might be once or twice a day. Busy boxes might be cleared at other times to avoid overflowing, and also to spread the work for the sorters. Extra clearances are made in the period leading up to Christmas, to prevent boxes becoming clogged with mail.
Since 2005, most Royal Mail post boxes have had the time of only the last collection of the day listed on the box, with no indication of whether the box is cleared at other times earlier in the day. The reason given for this by the Royal Mail is that they needed to increase the type size of the wording on the "plate" listing the collection times to improve legibility for those with poor sight and that consequently there was insufficient room for listing all collection times throughout the day. Some post boxes may indicate the next collection time by a metal 'tab' or dial that can be changed while the box is open. The tab displays a day or number, each number corresponding to a different time shown on the plate.
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