The rules that use the category "<np-gapsout_null-gapsin_null-unit-def-sing>" are:

<name_operation-gapsout_null-gapsin_np_gap>

<naming_verb> <np-gapsout_null-gapsin_null-unit-def-sing>

<np-gapsout_null-gapsin_null-unit-def-sing>

<np-gapsout_null-gapsin_null-unit-def-sing> <postnommod-unit>

<name_operation-gapsout_null-gapsin_null>

<naming_verb> <np-gapsout_null-gapsin_null-unit-def-sing> <unit_call_sign-gapsout_null-gapsin_null>