#### 13.4.1.1 refdes naming restrictions ¶

`lepton-schematic` will accept any string as a value for the refdes. However, some back-ends to `lepton-netlist` impose restrictions on the allowed syntax.

Specifically, `lepton-sch2pcb` requires:

- No spaces.
- No hyphens. This might upset the M4 macro language potentially used to generate footprints. “`_`” is OK.
- Any lower case suffix is ignored. This is so you can, place four discrete `NAND` gates on the schematic called `U1a`, `U1b`, `U1c`, and `U1d`. They will netlist into a single footprint named `U1`.
- Non-ASCII characters like ‘`ü`’, ‘`ö`’, ‘`ä`’, ‘`ß`’ will not print in pcb.