How to Transfer Attachments from One Sobject to Another One

Here I am giving an example to transfer attachments from Opportunity to case Sobject

 
List insertingAttachments = new List();
List deletingAttachments = new List();
for(Attachment atch :  [select id,name,body from Attachment where parentid = 'your Opportunity id' ]){
   Attachment  newattch = new Attachment();  
   newattch = atch.clone(false);
   newattch.body = atch.body; // required field
  newattch.name = atch.name;// required field  
  newattch .parentId = 'your Case id ';
  insertingAttachments.add(newattch); 
  deletingAttachments.add(atch);
}
insert   insertingAttachments;
delete  deletingAttachments