bolster

To bolster something is to prop it up so it stops wobbling. You bolster a friend's confidence with a few words at the door before their driving test, and a good photograph bolsters a shaky story.

The things you bolster are mostly things you cannot touch: confidence, morale, an argument, a claim, an economy, a falling currency. In writing about evidence it takes exactly that kind of object — new figures bolster the case for the bridge. There has to be something standing already; you bolster what is weak, you do not bolster something out of nothing. The word has a solid noun behind it too: a bolster is the long firm pillow that runs the whole width of a bed, under the soft ones. That pillow is the picture to keep — something firm pushed underneath to take the weight.