Onager - from above

In this picture you can see the two twisted skiens (white) and the
upright locking rod which holds the onager in the loaded position.
The firing trigger is the small green and white rod  extending from
 the bottom of the weapon base.

Onager -- (Catapult) Locked and Loaded

Onager (Catapult)
The Onager was used to throw rocks against a castle or fortification wall.   The
orange arm  is propelled by two loops of twisted skiens which when twisted
 tightly will eturn the arm and its ball rapidly against the upright and its
cushion.   This model which is about 9" long will catapult the wooden ball
about 25-30 feet 

Mantlet - side, front view

Mantlet - Side view

Mantlet - Rear view

Mantlet

Mantlet
This is a protection device for use in the field to protect the workers operating the siege machines.
Many of these were built and were moved into position to protect the soldiers and workers who were
an important part of the siege.

Provins. Tour de Ce'sar

Provins.  Tour de Ce'sar

Above a mid-twelth century castle.  It had an unsually shaped keep on a square base with four semicircular corner turrets.  I consists of twi levels.  The crenelated  wall that surrounds it is called a "chemise."

1. Wall extends down the motte and forms a gate;

2. Curtain (Chemise) Wall;

3. Allure (Wall walk);

4. Mound (Motte);

5. 12th Century Keep.

Orig. Sidney Toy. Mens. ETDELT. 1925