Group Only Door

Create a door, then place this script inside of the door.

--// Variables
local door = script.Parent -- Change if the door is not the parent of this script.
local groupId = 1234567 -- Your group ID
local minRank = 255 -- Minimum rank required to open the door

--// Functions
local function openDoor(hit)
    local character = hit.Parent
    local player = game.Players:GetPlayerFromCharacter(character)

    if player then
        if player:GetRankInGroup(groupId) >= minRank then
            door.CanCollide = false
            door.Transparency = 1
            task.wait(1)
            door.CanCollide = true
            door.Transparency = 0
        end
    end
end

--// Events
door.Touched:Connect(openDoor)