.pg !!
.lm CMDTAB.nf
 ________
|        |
|        |
|   .OP  |
|        |
|________|
.fi.lm LEFTMG
.hl 1;OP command
.ix OVERPRINT
.ix OP
The overprint command (OP) will overprint the previous line with the
specified characters.
.s.lm +7.nf
 _________ ___________________________________
|         |                                   |
|   .OP   |    [n] [;text] or                 |
|         |    text on following line         |
|_________|___________________________________|
.fi.lm LEFTMG.s
The OP command will overprint the previous line with the text.
.b
The parameter n, is optional and is an indentation count.
Like the center command, the text for OP can appear on the same line as the
command, when preceded by a semi-colon, or it can be placed on the line
immediately following the OP command.
.s 2;.lm LEFTMG
Defaults:
.s;.lm +7
Default indentation is 0.
.b.i-7
Notes:
.b
This command is typically used in equations to generate the center line of
displayed equations. See EQ.