[Oroaranion]

You never know, Leggy could have been preparing the table for Aragorn and Theoden's return, so they could have a little victory feast. And in his hurry, he tipped the table over, instead of just clearing whatever junk was already on it.

But most likely, he was getting the bench to barricade the door. if you took any attention to the previous scene, there were hunreds of Uruk-Hai trying to break the gate down.

Have you also noticed that Gimli is not involved in the following fracas, because he disappears to blow Helm Hammerhand's horn. He must have long breath, because I'm sure that the horn never stops making a noise.