---
title: On using stacks
card_id: 2465
---

### On using stacks

You use the `start using` an`d stop using `commands to insert stacks into the message-passing path.

* You can insert up to 16 stacks into the      message-passing path.

* If you start using a stack that’s already in     use, HyperCard brings it to the front of     the list of stacks in use.

* You cannot compact a stack that’s      being used.

* Handlers  can act only on the objects in      the current (or active) stack. 

   For example, if an executing handler in a    stack added to the message-passing path    refers to field 1, but the current     stack doesn’t have a field 1, you’ll get a     script error.