When I upgraded to Tajima  Illustrator Extreme I was upset to find that the End Lock list no longer included Triangle & Diamond, it just had Basic and Line. When I reported it I was questioned why I needed them.

Being new to the business it made me wonder how and when I should really be using them.

What upset me about the missing diamond was I like to use the diamond at a big size stitch (2 or 3 mm) for locking off temporary tensioning or holding stitches as its easier to cut them out afterwards.

The Line lock is my default general purpose lock as I find it useful for hiding in the end of satin / steil. But I also find that it stresses the fabric and can cause a pucker or even tear, particularly on weaker and stretch fabrics and especially if placed at the end of a satin or on a corner (I always move it back away from ends and corners now)

Diamond and Triangle I use to avoid stressing an aukward fabric, and if necessary will put them on top of the satin stitch at the end (yes I know it shows slightly but I reckon its far better than tearing a hole in a shirt after an hours stitching)

I also use 1 or 2 mm diamond and triangle for start and finish of sequin stitches as I use the very fine nylon monofilament which is a single strand so cannot pass through itself to lock, and pulling it tight in a small default 0.6mm line lock appears to overstress almost any fabric.

So when and how should I really use the different lock stitches ? ? ? ? ?

It looks to me that the diamond and triangle lock stitch types were removed by accident.  We wanted to remove them from sequin segments but it looks like we removed them from all segment types.  I will try to get this back in the next maintenance release.

The line lock stitch type is recommended for smaller columns because it reduces the chance of sticking out of the shape. 
The basic lock stitch is better if the columns are a bit longer.  The benefit is that it stitches like a bow tie.  This kind of shape locks better and makes sure the stitches do not go back over the same stitch penetrations reducing thread breaks.  I would use the Basic lock stitch type unless the lock stitch sticks out.  In these cases I would use the line lock stitch.

The diamond and triangle lock stitch types are similar to the basic lock stitch but might be better with particular shapes.  
The idea with the lock stitches is that you want  3-4 stitches in a configuration that holds the thread down before or after a trim.

Best Regards,

I use the basic lock the most personally.  It has 5 strokes and looks like a tiny bow tie.  It is more intrusive than the line lock but holds a fill better.  I use lines on small letting. 

If I am hand-punching my own underlay, I create my own lock and it looks like a star.  Then I'll use the basic lock to tie off with.  I don't do sequins so can't speak to that.

 I'm totally into the line lock, almost all of the time.

Why is that?

Well, for one, I tend to lean toward the confection industry where that kind of lock have been in use all the time. Practically all things being sewn have a line type of lock stitch. Secondly, I have made a lot of testing and find that a line lock in at 0.5 or 0.6 mm length makes the top thread catching up with bobbin thread effectively and with a minimal disturbance of fabric and very little buildup of stitches that might be visible through the top stitching. I also use the line lock at end of segments with a stitch length of 1 mm in order to perform nice stitches and have found it to be enough for locking down. Never have any problem with unraveling at all.

I do use the basic lock at segments less than 2 mm wide but that's practically all I use it for.

As you can see, there are many different thoughts and ways to work with digitizing and what's works for you is the right way to go. Every digitizer have his/hers own way of doing things and whatever way we choose, it's chosen by experience, trial and error, learning from others or simply just by chance. There are no true answers to any of the "how to" questions...

Happy digitizing

thanks everybody

It looks like I'm in a minority using the diamond and triangle, but then I've always done things differently.

There must be some reason they put them into the software originally, . . . it can't be just for me?