Elements may be removed from the stack using the Pop method:

$stack.Pop()    # This returns Under the bridge 

If the stack is empty and the Pop method is called, an error will be thrown, as shown here:

PS> $stack.Pop()
Exception calling "Pop" with "0" argument(s): "Stack empty."
At line:1 char:1
+ $stack.Pop()
+ ~~~~~~~~~~~~
    + CategoryInfo : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : InvalidOperationException 

To avoid this, the Count property of the stack may be inspected, for example:

# Set-up the stack 
$stack = New-Object System.Collections.Generic.Stack[String] 
"Up the road", "Over the gate", "Under the bridge" | ForEach-Object { 
    $stack.Push($_) 
} 
# Pop from the stack until the stack is empty 
while ($stack.Count -gt 0) { 
    Write-Host $stack.Pop() 
}