Don't know of any formal tutorial. Similar to your pen issues, knockouts will block out anything drawn earlier in the file. You can use the move to front command to move an item to the front of the list, so a knockout will blank it out. Uses I have found: Elevations. Instead of voids or tracing around windows, I now have the first thing in my window symbol is a polyline with knockout on. Then any siding/brick/etc is blocked or knocked out. My hatch layer is one of the 1st layers now in the list. Elevations. Have a guardrail in front of windows and siding. Make a Guardrail layer at the end of the layers, draw up the guardrails with polylines, knockout on. Now you can view/print an Elevation with or without the Guardrail and it looks great. Floor Plans - Stiars - Draw the treads full width, then later draw the handrail as a polyline, and it knock's out the tread below the handrail. Floor plans - Want to show floor tile? Have the Water Closet and Lav symbols have a polyline to knockout the tile grid at the fixture. Sometimes in my symbols, I add a layer at the start, call it KO and place the knockout polyline there. Text and Dimensions can have KO turned on so the text over the hatch can be read. I'm sure others have other uses for this feature.
Roger Donaldson AIA CSI CDT NCARB abUsing Datacad since 1986, ver 23.00.01.02 (SE) http://www.RogerDonaldsonArchitect.com
Looks like a great feature...very similar to layer mask in photoshop. I've used it already on a porch post.
Knockouts can be accessed through the Curves menu and through the text menu...any other areas I should look for them? Trying to convince a colleague to upgrade from V11...I think a good explanation of KO's would be just the ticket for him!
