A blind Samson is still a crafty Samson. He is not totally defenseless. He is standing between the pillars. And he seems to know something of the structure of the temple. He wants to take advantage of the fact that these pillars supported the entire temple. He asks the young man, Let me feel the pillars on which the house rests, so that I may lean against them.
Maybe Samson just wants to regain his balance and catch his breath, because he is tired from grinding grain. We need to keep reading to see why he asked to feel the pillars.
26 And Samson said to the young man who held him by the hand, “Let me feel the pillars on which the house rests, that I may lean against them.”