Hi mariamurr
- Create the document size 150 wide by let's say 20 cm. but make sure you got the measurement units set to cm. no px
- place 2 guide lines one in each side of the document, as it's specified, one of them must be placed 2 cm in one side, and 1 cm on the other. So you will end it up whit a 147 cm wide to work whit, right. "150-3=147"
- Now we already know that size each pattern of the is gonna measure 49 cm wide by "147/3=49"
- Now for the easy part. using your ruler tool "I" we are going to measure those 49 cm needed for the first pattern, whit the ruler tool selected position the cursor on one of the guidelines that we've settled before "those 1 or 2cm margins, remember "
- Holding the "SHIFT", click and drag the mouse across until you see that you have the 49 cm required, "take a look in the ruler palette tools on top right below the main menu, any time you drag one of the ends of the ruler measurement line you will see the values changing, on the different axis XYZ, WH,A,L1,L2" the one we are interested in is the L1 axis, that value will show you the length of the space being measured using the ruler, when you see that you got the 49 cm or a pretty close approximation just let go on the mouse button, and you got your first pattern length.
- Now like we did before click and drag a guide line to that position.
- Do the same thing for the last guideline "once you got the ruler set to 49 cm for the first position, you can just click and drag your ruler to the next one holding "SHIFT" and draw your last guideline"
- Finally just create the pattern and position it over the guidelines along the document.
I've added the PSD file as reference
Hope this helps
