If you show consecutive alpha-carbons (but not the other backbone atoms) they are automatically connected by lines.  You don’t have to do anything else. For example:

open 121p

hide cartoon

show @ca

hide @n,c,o

See image attached below for the result.  Tested in ChimeraX 0.9 release.

The CA-CA lines are actually pseudobond sticks but thinner than the “real” bond sticks.  You can make them fatter if you want.  In this example, if you look in the Models panel, this pseudobond model is #1.2 chain trace.  Here is an example command to make them fatter:

size #1.2 pseudobondradius .2

<http://rbvi.ucsf.edu/chimerax/docs/user/commands/size.html>

I hope this helps,

Elaine

On Aug 21, 2019, at 7:39 AM, Yazan Abbas <yazan.abbas@gmail.com> wrote:

Hi, 
While looking  through the user guide, I came across an option to draw a line between consecutive Calphas that are displayed. I made a mental note to use that option in my figure, but I failed to bookmark it or write down what the command was. I've been through the user guide several times again, but can't seem to find it. Would appreciate it if someone could jog my memory.
Thanks, 
Yazan