\UseTextAccent & \UseTextSymbol

Synopsis:

\UseTextSymbol{encoding}{cmd}

or:

\UseTextAccent{encoding}{cmd}{text}

Use a symbol or accent not from the current encoding.

In general, to use a fontenc command in an encoding where it is not defined, and if the command has no arguments, then you can use it like this:

\UseTextSymbol{OT1}{\ss}

which is equivalent to this (note the outer braces form a group, so LaTeX reverts back to the prior encoding after the \ss):

{\fontencoding{OT1}\selectfont\ss}

Similarly, to use a fontenc command in an encoding where it is not defined, and if the command has one argument, you can use it like this:

\UseTextAccent{OT1}{\'}{a}

which is equivalent to this (again note the outer braces forming a group):

{fontencoding{OT1}\selectfont\'{\fontencoding{enc_in_use}\selectfont a}}

Here, enc_in_use is the encoding in force before this sequence of commands, so that ‘a’ is typeset using the current encoding and only the accent is taken from OT1.