How did Ehud bypass Eglon's security check?

[TonyChanYT]

Judges 3:

15 Then the people of Israel cried out to the LORD, and the LORD raised up for them a deliverer, Ehud, the son of Gera, the Benjaminite, a left-handed man. The people of Israel sent tribute by him to Eglon the king of Moab. 16And Ehud made for himself a sword with two edges, a cubit in length,

1.5 ft or 45 cm, short enough to hide it

and he bound it on his right thigh under his clothes.

Most people were right-handed. They would hide their swords on the left side for easy drawing. Apparently, Eglon's security people checked Ehud's left side for weapons and found none, missing the weapon hidden on his right thigh.

17 And he presented the tribute to Eglon king of Moab. Now Eglon was a very fat man. 18 And when Ehud had finished presenting the tribute, he sent away the people who carried the tribute. 19 But he himself turned back at the idols near Gilgal and said, “I have a secret message for you, O king.” And he commanded, “Silence.” And all his attendants went out from his presence. 20 And Ehud came to him as he was sitting alone in his cool roof chamber. And Ehud said, “I have a message from God for you.” And he arose from his seat.

God probably had interfered with the security check so that Eglon's guard would not have noticed the hidden dagger.

21And Ehud reached with his left hand, took the sword from his right thigh, and thrust it into his belly.