The eye of the needle was a small door that was usually built into the gates of a city.
ie. The entrance to a city such as Jerusalem would have massive iron bound defensive gates set in the wall with huge towers either side to protect them. These city gates would be closed when under threat, or at sundown every night for safety.
If someone arrived after sundown, it would be up to the discretion of the gate keeper whether he would let them in at all, or make them wait outside till dawn. However even if he did allow them access, it would only be through "the eye of the needle".
The eye of the needle was the tiny man sized door that can be seen in the middle of the big gates. The gatekeeper would only open the eye of the needle because it was more than his life was worth to open the main city gates. He would have no idea whether the lone traveller didn't have 500 armed men hiding in the dark to rush past him.
If a caravan of camels arrived after sundown, they would be desperate to access the city for safety. Loaded up with all their trading wares it would be impossible to get through the door. However if all the burdens were unloaded, the naked camel could squeeze through the tiny door by bowing down onto its knees.
Need I say more? Entering the kingdom of heaven, naked and on our knees is about right. Nothing we possess, whether hard earned riches, or declarations of self righteous poverty.
Nothing will aid our access other than humility before God's righteousness.