Sub-grids, such as Custom Objects ("Line Items"), Contacts, Tasks, etc. can be added to or removed from the layouts of record types.
NOTE: This functionality requires Add/Edit Access to the Type Manager - Manage Sub-Grids feature in Role Permissions.
Follow the steps below to add Sub-Grids to a layout:
From the homepage, click 
to open the Application Settings, then select 
from the Settings menu.
From the Object Type drop-down, select the object and type you want to add the sub-grid object to. For example, to add a custom object line item sub-grid to SOW contracts, select Contract and then SOW.
When the layout opens, scroll to the bottom of the Fields list and click Grids.
Click to select the grid(s) you want to add. Selected grids will be marked with a check mark and added to the layout. Once on the layout, you can drag the grid to a new location. To remove a grid, open the Grids list and click to de-select.
You can modify the default appearance of sub-grids inside records:
Select or de-select columns as desired from the Columns drop-down
Change the width and/or the order of the columns
Set the number of visible rows by selecting an option from the #Rows drop-down (3, 5, 10, 15, 20 or 25 visible rows)
Once finished configuring the Sub-Grid, click 
.