Use the HM move Cut on the door. (Might be thinking of the other base.)
The rocket team are not on four island. there are two grunts up a ways of Mt. Ember north of one island, however the Rocket Base is on five island. It requires two passwords if you want to enter. Work that bit out for yourself.
First you go to the dotted hole on six island and get the ruby. Then a scientist will take it and give you the second password to the team rocket base, then go to five island to the team rocket base. Go threw it and find the scientist, u must battle him. after u beat him he will give it back.
Use the HM move Cut on the door. (Might be thinking of the other base.)
There is no team rocket base in Blue Rescue team. Unless you name your team Team Rocket.
You have to defeat the elite 4 and have the national dex,then you go to 1 island and go the farthest you can,then get close to the team rocket goons and they should tell you a password,later a scientist gives you the other password on 6th island
The team rocket base is in Mahogany town.
The Team Rocket warehouse is in the Goldenrod Tunnel, but you have to get the key first which is obtained from a Team Rocket member in the 5th Floor of the Radio Tower.The same way in Soul Silver: after you get the seventh badge, Team Rocket will have taken over the Radio Tower in Goldenrod City. Team Rocket is defeated when you rescue the Director and beat all four Rocket Executives.
The lift is in the team rocket base
after beating the team rocket executive the murkrow knows the answer and you need to follow it through the base to the door
It is underground
By this point you will have both the passwords required for the Rocket Base on Island 5. Head to Island 5 and go through the Rocket Base, the Scientist is there.
You don't on Island 6. You head to Island 5 and the rocket base where you will find him and the Sapphire.