How do I merge two lines?

How do I merge two lines (which share a common endpoint) into one line?

Use a Style which displays ‘end-points’ to make them easier to see…
With nothing selected, use the Move Tool on the colinear vertex and drag it to one of the other ends…

‘FredoTools’ includes a ‘Remove-Lonely-Vertices’ tool…
Useful if you have lots of them…
See this:
The download is here:
You also need to install the latest LibFredo from here:

are the two lines going in the same direction (as in- it looks like the two lines should be one single straight line)

or- do the lines have an angle in them and you’d like to join them into a single polyline?

Both, I wanna merges lines that are on the same “line”, and lines that have an angle to eachother. I seached my head off in the Sketchup programme, but couldn’t find a button. Interestingly, there is a button to split lines, but there seems to be no button to merge them again (?!). I’m not too interested in plug-ins and stuff, as this thing is so essential that I prefer to wait till they put in a ‘factory installed’ button. Thank for the replies so far …

well, you need to ‘weld’ the lines and you’ll need to use plugins to do so… I suppose you can keep waiting though.

the split option is for… not sketchup.

If you have two colinear edges butted end-to-end, draw a third edge from the common endpoint to anywhere, then erase it. The original two edges will now be one, with the extra endpoint gone.



Jeff I think he might be referring to Explode Curve.
Gully that’s a useful tip not many people realise works, but not so handy on a fully exploded curve.

Steven saying you don’t want to use plugins is understandable in some ways, but limiting yourself by not even downloading a tool that most would argue should be part of the standard tool set is a bit self defeating.
You can quickly install Weld from the extension warehouse and save yourself lots of time.

Sorry, was a bit childishly stubborn there. Have in the meantime installed
"Weld’. It appears under ‘Extensions’ in the menu, so I guess it’s properly
installed. Only, when I select the two lines (in this case, they’re
segments of the same Arc, with of course a common Endpoint) and then click
on ‘Weld’, NOTHING happens. Tried tweeking all the possible setting options
of the Weld plug-in, to no avail …

Let’s backtrack a little…
You have two segments of an Arc.
Why would you want to ‘weld’ those edges ?
‘Weld’ tools simply takes a selection of edges that meet at end vertices, they can be either simple ‘lone’ edges or edges that are bound into an arc or other curve object…
‘Welding’ them combines them into a single bound curve [they then all select in one click].
It cannot weld edges that ‘branch’ - because as you know an edge coming into a curve splits that curve where it touches anyway.
Welding two Arc segments will at best only make a new Curve with two segments, it looks like an Arc but it now has no radius etc - an Arc is a special subset of Curve… It may even leave it as a 2 segment Arc ?

If you have Exploded the Arc into its separate edges, then you can recombine them into a single bound curve using a ‘weld’ operation. It will not be an Arc.

If you use a Style that shows end-points you should not see the ends of the segments that form an arc or curve [you will see just the start/end of the whole ‘curve’].
If you do it is no longer one object.

All of this still begs the question… what do you want to do this ?

Perhaps if you pasted a screenshot of what it is you have we might understand better and thereby help you better…

Thanks for the tip, Gully, and it works indeed, that is, for simple, colinear lines.

However, my situation is that of an arc (consisting of about 12 sub segments) cut in two separate lines. So it looks like a normal arc, but when you select it, only half turns blue. Don’t know how it happened, probably when I constructed it using an aid line or something.

And that’s what I want to change. It schould entirely turn blue. I don’t think your method would work.

Tig’s asking all the right question and as I hadn’t used that specific version of weld I installed it and tested.
And here it is welding segments together.

It gets complicated indeed, but there seems to be a misunderstanding. There’s no ‘branching’. I just drew a simple Arc. The middle of it had to pass through a certain point in space. Couldn’t find a way to fix that point using the guide line or protractor tools, so I drew a temporary edge, and then drew the midpoint of that arc through the endpoint of that edge. Of course, afterwards I deleted the temporary edge, and the rest is history: the arc now consists of two separate lines.

For my purpose it needs to be a single line, because the intention is to draw 3 parallel arcs so I can form a solid body. Then I’m gonna move one of the rectangular end faces of that body while the other face stays put, to deform the body. If one of the arc edges does not consist of a single line, I’d get an awkward knack halfway the body …

Thanks for the Vid.

Did exactly that: clicked to select line one ( = 6 segments of the arc), then shift + clicked to select line two (selected the other 6 segments of the arc). So arc was entirely selected. Then went to ‘Extensions’ and then clicked on ‘Weld’. Nothing happened. Still two separate lines …

BY THE WAY, tested ‘Weld’ on two simple colinear lines, and it works …

The only thing I can think of is that there is the tiniest of gaps or a bit of your helper line between the endpoints of your two arches. I have an old version of Weld in my SketchUp 8, and it had no problem welding two arches with a common endpoint.

BTW, if you had made a group of your helper lines before drawing the arc, it wouldn’t have split it in the first place


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The edges must all touch…

Switch all layers ON.
Switch View > Hidden Geometry ON.
If you have ill-advisedly put some geometry in an ‘off’ state but left in the same context as your arc it will continue interact with the new arc.
Layers/hiding does not separate geometry if merely makes it unseen - use groups or components and assign them off layers to do the same thing AND avoid unexpected interactions…
That is possibly why it’s in two pieces…

An arc does not spontaneously split.

Of you select the pieces of the arc, and there are no branching edges [hiding an edge does not stop it’s interaction with other geometry in its context] - then they should all weld into a single curve.
It will look like an arc, but it will actually be a ‘curve’ !
To get a complete ‘arc’ you need to ensure there are no hidden intersecting edges and them remake the arc from scratch…

We have come along way from the original question…
It has been like ‘pulling teeth’ as we say where I come from :wink:

Gee, guys, could I possibly have been more explicit about the circumstances under which my “tip” works? Obviously, it doesn’t pertain to an exploded curve or two otherwise non-colinear edges.

And Steven, as TIG mentioned, your original question could certainly have been asked with more precision. As you phrased it, it might have been referring to colinear edges. In other words, you’ve led us on a merry chase, which is a saying where I come from.


Ok, next time I won’t bother ‘liking’ your tip or wording my reply to include it.

Dear all

Sorry for raising the spirits with my “unprecise questions”. In the mean time, I’ve moved on (or should I say, buggered off), but not without discovering the CULPRIT.

It turn out there was an esoteric, plasma-like Endpoint (without a line attached to it!) floating in space. I discovered it by accident when, after I had entirely erased the Arc, the Guide Line Tool kept snapping to a point in empty space, right where the separation point in the Arc had been. I framed the area with a Selection Rectangle, but nothing showed up. Then I resorted to the Eraser Tool, which indeed also snapped to it, and I immediately pulled the left-mouse-button-trigger, sending it to its demise. Thereafter I redrew the arc, and the problem was no more

Don’t know where it came from. I never used Layers in the project, so it couldn’t have come “from another dimension”. I owed you this account after all your efforts.

Thanks again


This is an old conversation but I found your answer simple and elegant and just what I needed. I had two connected lines that I needed to be one.

Thank you!

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Great tip Gully!!! Thank you.

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