Hi

This is already in place in Inkscape.

a. Draw the tickmark,
b. select the tickmark (F1)
c. Show the rotation center (Shift S)
d .Drag the rotation center straight down (hold the ctrl key down while dragging to "lock" the movement.)

e. Click the tickmark,
f. Make a duplicate (Ctrl D), click the duplicate until you get the rotation mark,
g. Press ctrl and rotate the tickmark around the new center, It will snap every 15 degrees, you can change the number in the preferences

Repeat step f and g to get the rest of the tickmarks.

When you get the hang of this you can use tiled clone to make all the tickmarks in one go.

Have fun.

Thanks, but we have to do this manualy, spet by step...
In some softwares I used, in the rotation tool, you can chose the degre and it's possible to check a box named "occurences" and an other box named "number".
It's very easy to use.
This option is also avalable in translation tool...
Anyway, your solution works !
Thanks for your answer.

After d.), you can make tiled clones.

P1 symmetry,
1 row, 12 column,
-100% x offset on columns,
30° rotation for columns.

http://tavmjong.free.fr/INKSCAPE/MANUAL/html/Tiles.html

Hi, yes, I used this method !
I just thought that a option in the rotation tool could be simpler, but there are other way to get to what I want.
Thank you anyway for your help !