MATCHPROP pushes the properties of a source object onto other objects. SIPHON does the opposite: it reads colour, layer, linetype, lineweight and linetype scale off one picked object and makes them the current defaults, so everything you draw next inherits them.
What PropSiphon does
It sets CECOLOR, CLAYER, CELTYPE, CELWEIGHT and CELTSCALE from the object you pick.
The use is obvious once you have it: you are about to draw something that should match a thing already on the drawing, and rather than reading its properties and setting five controls, you point at it.
How to use it
- Load the routine with
APPLOAD, or put it on your support file search path. - Type
SIPHON. - Pick an object whose properties you want to draw with.
- Draw. Everything new inherits them.
How it works
A DXF group is only applied when the object actually carries it. An object set to BYLAYER simply has no group 62, 6, 370 or 48 entry, and in that case the corresponding default is deliberately left alone rather than being forced.
That restraint is the considered part. Reading a BYLAYER object and then setting the current colour to something explicit would be a misrepresentation — the object does not have a colour of its own, it takes its layer’s. Leaving the default untouched is the honest translation of what was picked.
Notes and limits
- BYLAYER properties are not forced. If the picked object inherits a property from its layer, your current default for that property is left as it was.
- It changes your drawing defaults, not any object, so there is no undo group — nothing in the drawing changed.
- The layer changes too. That is usually wanted, but it is the setting people forget they applied.
Download and details
| Name | PropSiphon — adopt a picked object’s properties as the current defaults |
| Download | PropSiphon.lsp — 6.1 KB, plain AutoLISP source. Downloads directly; no zip to unpack. |
| Type | AutoCAD AutoLISP routine |
| Command | SIPHON |
| Requires | nothing beyond a CAD platform with AutoLISP. |
| Source size | 6.1 KB, 138 lines |
| Error handling | Yes — a *error* handler restores every system variable it changed, on cancel as well as on error. |
| Undo | Not needed — this routine only reads the drawing and changes nothing. |
| Compatibility | AutoCAD (any release with AutoLISP), BricsCAD, ZWCAD, GstarCAD, ProgeCAD and other IntelliCAD-based platforms. AutoCAD LT needs a LISP enabler. No .NET, no ObjectARX, no installer. |
| Author | YZ, August 2026 |
| Licence | Free to use, supplied “as is” with no warranty. |
References
- LAYERPILOT LISP — automatic layer switching, so defaults matter less
- SL LISP — set just the current layer by picking an object
- More free AutoLISP routines on this site
- Wisey’s Steel Shapes — free structural steel section drawing program