About the Placeholder Assembly
When you insert a manikin (click > 
Insert Manikin), the Open dialog box and the Place Manikin dialog box open. The Use placeholder check box is selected by default in the Place Manikin dialog box. If you do not clear the check box, you will create a placeholder to host the manikin during your session.
Insert Manikin), the Open dialog box and the Place Manikin dialog box open. The Use placeholder check box is selected by default in the Place Manikin dialog box. If you do not clear the check box, you will create a placeholder to host the manikin during your session.A placeholder simplifies the handling of manikin-related data. Because the manikin itself is a read-only assembly, all its attributes and postures (including the manikin's specific center of gravity and other data not visible in the user interface) are stored in the placeholder. This data defines the manikin as a unique element of the design assembly. When there is no placeholder, the manikin's posture is stored in a higher level assembly.
If you intend to place the same manikin a number of times in the active assembly or elsewhere, clear the Use placeholder check box. A placeholder is not created for the manikin, and a default Center of Gravity (COG) analysis is not performed. Use the standard > 
Mass Properties tool instead. The Center of Gravity appears in the results.
Mass Properties tool instead. The Center of Gravity appears in the results.When you insert a manikin using a placeholder assembly, you can:
• Control accidental changes to the original library manikin. If you modify a library manikin, you must save it as a different manikin.
• Create a different manikin with a unique name and special attributes. It is easier to store the different attributes in a placeholder rather than modifying a library manikin assembly.
• Run a COG analysis internally.
When you copy and paste a manikin, you must select an assembly level according to the design intent:
• To copy a manikin and keep the manikin's current posture, use a placeholder (or higher level assembly).
• To copy a manikin without the current posture, select and copy the manikin assembly itself.
Use the Creo constraints and placement interfaces to manually add accessories to a manikin. These accessories are treated as separate components and are also used to calculate the COG. Insert the accessories as components of the placeholder assembly and do not modify the manikin assembly itself. When you replace the manikin assembly with another, all the accessories stored in the placeholder can be transferred to the new manikin.