This tool can turn on/off a special no-zoom crosshair, which is available for all sniper weapons in CS 1.6 (same crosshair as for all weapons, from now also for awp, scout, sg550, g3sg1). This will help you to aim with snipers when perfoming quickscopes or noscopes etc.
If you're playing in competitions, ESL etc. you have to play with default models for your weapons. This means .. no no-zoom crosshairs. Otherwise you could get a ban for that. But if you play on public servers, you can train yourself with that crosshair. Steam/non-steam servers will not ban you for that.