Opticsbuilder: adding apertures === We'll continue from the [previous tutorial](https://codimd.web.cern.ch/s/WXDIi98MP). # Manually adding aperture You can just type an aperture type and parameter in the table. - no aperture data: aperture will be asssumed the last row with value - circle: param1 is radius, optional param2 is ellipse second half-axis - racetrack: param1 is horizontal half-axis, param2 is vertical half-axis The last known aperture will be kept for the whole exported region (for a constant aperture, filling the first line is enough)  Before exporting, define how often to split a curve:  Specify the filename and export:  # Inserting in Synrad Use the File -> Insert geometry -> To current structure command:   # Using custom apertures       # Adding custom apertures [Documentation for custom aperturtes](https://molflow.web.cern.ch/node/364)