Recently images have been posted online showing the use of the 122mm rockets fired by the BM-21 Grad being used by groups belonging to the Syrian armed opposition, including this photograph from Jabhat al-Nusra
As you'll note, this is not the usual firing platform for a 122mm rocket, but a series of videos posted by the Syria Martyrs Brigade (Shuhada Souria) shows that this isn't the only example of a 122mm rocket being launched in less than ideal conditions
As Peter Bouckaert of Human Rights Watch stated during the Libyan conflict "the Soviet-made Grad in particular is one of the world's most inaccurate rocket systems", and I'd imagine propping the rockets up against rocks and trees instead of using a BM-21 Grad to launch them does nothing to help their accuracy, and makes their usefulness rather questionable.
Update February 16th It now appears the opposition has dropped trees as their launching platform and have instead opted for a DIY launcher, which can be seen in the below video
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