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\hss

Synopsis:

\hss

Produce a horizontal space that is infinitely shrinkable as well as infinitely stretchable (this command is a TeX primitive). LaTeX authors should reach first for the \makebox command to get the effects of \hss (see \mbox & \makebox).

Here, the first line’s \hss makes the Z stick out to the right, overwriting the Y. In the second line the Z sticks out to the left, overwriting the X.

X\hbox to 0pt{Z\hss}Y
X\hbox to 0pt{\hss Z}Y

Without the \hss you get something like ‘Overfull \hbox (6.11111pt too wide) detected at line 20’.