How to declare / override Magento Blocks

<!-- ************************************************ -->
<!-- BLOCKS / DECLARE -->
<!-- ************************************************ -->
<!-- structure:
		Unexpectedit/Home
						/Block
							/*
-->
	 <global>
	    <blocks>
	        <home>
	            <class>Unexpectedit_Home_Block</class>
			</home>
	    </blocks>
	</global>
<!-- ************************************************ -->
<!-- BLOCKS / OVERRIDE -->
<!-- ************************************************ -->
<!-- structure:
		Unexpectedit/Catalog
							/Block
								/List
									View.php
									/List
										Toolbar.php
-->
	 <global>
	    <blocks>
			<catalog>
		    		<rewrite><product_view>Unexpectedit_Catalog_Block_Product_View</product_view></rewrite>
		    		<rewrite><product_list_toolbar>Unexpectedit_Catalog_Block_Product_List_Toolbar</product_list_toolbar></rewrite>
			</catalog>
		</blocks>
	</global>
<!-- ************************************************ -->
<!-- BLOCKS / OVERRIDE / Admin -->
<!-- ************************************************ -->
<!-- structure:
	Unexpectedit/Adminhtml
						/Block
								/Customer/Edit/Tab
												Account.php
-->
	 <global>
        <blocks>
            <adminhtml>
            	<rewrite><customer_edit_tab_account>Unexpectedit_Adminhtml_Block_Customer_Edit_Tab_Account</customer_edit_tab_account></rewrite>
            </adminhtml>
        </blocks>
    </global>

Tags: blocks, create, declare, Magento, override, overriding, syntax, xml