Trigger to share the record level access to User.

    trigger Account_PrivateAttachmentSharing on Account (after update)
{
  /*
    When the Owner of an Account is changed, create
    a sharing rule for each associated Private Attachment record.   
  */
  Set<Id> accIdSet = new Set<Id>();
  for (Account acc : Trigger.new)
  {
    if (acc.OwnerId != Trigger.oldMap.get( acc.Id ).OwnerId)
    {
      accIdSet.add(acc.Id);
    }
  }
 
  if (accIdSet.size() == 0)
  {
    return;
  }
 
  //## get all private attachments related to all of the opps...
  Map<Id, List<Private_Attachments__c>> accIdPAMap =
          new Map<Id, List<Private_Attachments__c>>();
 
  List<Account> accWithPAList = [Select Id, Name, OwnerId,
        (Select Id From Private_Attachements__r)
        From Account o
        WHERE o.Id IN :accIdSet];
 
  /*     
  List<Private_Attachment__c> paList = [SELECT Id, Name
          FROM Private_Attachment__c
          WHERE Opportunity__c IN :oppIdSet];
  */

  List<Private_Attachments__Share> paShareInsertList =
          new List<Private_Attachments__Share>(); 
  for (Account accpa : accWithPAList)
  {
    List<Private_Attachments__c> paList = accpa.Private_Attachements__r;
    if (paList != null && paList.size() > 0)
    {
      for (Private_Attachments__c pa : paList)
      {
        //## have to update PAs for this Opp...
        Private_Attachments__Share pashare = new Private_Attachments__Share();
        pashare.ParentId = pa.Id;
        pashare.UserOrGroupId = accpa.OwnerId;
        pashare.AccessLevel = 'Edit'; 
        paShareInsertList.add(pashare);
      }
    }
  }
 
  System.Debug('    #### paShareInsertList: '+paShareInsertList);
  //PrivateAttachmentOwnership.insertRecords(paShareInsertList);
  try
  {
    Database.insert(paShareInsertList, false);
  }
  catch (Exception e)
  {
    //## an error will be thrown if it's a dup record...
  }

}