ACL Manipolation

Add-ItemAccess.ps1

function Add-ItemAccess{
    [CmdletBinding()]
    param(
        [Parameter(Position=0, Mandatory=$true, ValueFromPipeline=$true)]
        [ValidateNotNullOrEmpty()]
        [Sitecore.Data.Items.Item]$item,

        [Parameter(Position=1, Mandatory=$true)]
        [ValidateNotNullOrEmpty()]
        [string]$roleName)

  $myRole = Get-Role $roleName
 
  # Get the current accessrules
  $accessRules = $item.Security.GetAccessRules();
 
  # Apply read access for the "roleName " to the current item
  # and all it's children
  $accessRules.Helper.AddAccessPermission($myRole,
     [Sitecore.Security.AccessControl.AccessRight]::ItemRead,
     [Sitecore.Security.AccessControl.PropagationType]::Any,
     [Sitecore.Security.AccessControl.AccessPermission]::Allow);
 
  # Write the rules back to the item
  $item.Editing.BeginEdit();
  $item.Security.SetAccessRules($accessRules);
  $item.Editing.EndEdit() | Out-Null
}

#Now you can simply pipe items into the function as follows (item /sitecore/content/home item (rights cascading)):
Get-Item master:\content\home | Add-ItemAccess -RoleName sitecore\Designer