The Never Delete token is used to specify that the textbox containing this token, should not be un-intentionally (ie. caused by the outside days setting of monthly grids). However, intentional deletions using zap tokens or macro actions or Sara actions override the [||] token.
Always make sure that the [||] token is the first token of a textbox.
One example of this token's usage would be if a by-line of a monthly grid referred to some dates in the following month. Without a Never Delete token this by-line would be deleted with all the other outside days.
Note that this is example is not as common as one might think, since references to dates in the following or preceding months are usually done through MiniCalencar tokens or duration tokens, all of which have mechanisms to refer to other months while keeping a DayValue squarely in the current month.
Another example of the use of Never Delete tokens is in the sample grid on the right, where it appears that the shading of the textboxes is changed for outside days.
In reality, the GridTemplate corresponding to that sample has white textboxes under the regular textboxes for the DayValues where it is possible that an outside day may occur (ie. DayValues of 1-7 and 29-42). A Never Delete token was placed in each of these white textboxes, so that on outside days when the regular boxes are deleted, the white boxes are revealed.
The Never Delete token prevents the deletion of the current textbox.
If you wish to also prevent the formatting associated with outside days options from being applied to one or more specific tokens, then you should use the ignore outside days suffix, applied to individual tokens.