Roman Era, 500 BC–300 AD Roman padlock with chain The lock body is about 4 cm long and made of iron plate with a 6-cm round perforation. The mechanism consists of a horizontal metal bolt with a spring. The bolt slides from side to side to open and close with the turn of a key. Instead of a shackle, the lock has a metal chain attached on one short end, which is locked by the bolt in the other. This picture is a reconstruction of some padlocks that archeologists have unearthed in Saalburg, the citadel at the Roman Limes, built to hold off the barbarian invasions. Today Saalburg is a museum 30 km north of Frankfurt am Main in Germany. Similar locks are also on exhibit in two other German museums, Germanisches Museum in Nuremberg and Römisch – Germanisches Zentralmuseum in Mainz. Roman padlock with shackle and ward springs This padlock consists of two parts, a square lock body and a separate shackle with ward springs. The lock opens when the key is inserted through a narrow opening in the short end of the lock body, compressing the springs so the shackle can be pulled out. This type of lock is known from archeological digs in various parts of the UK. Roman padlock Like the previous lock, this lock has two parts: a square lock body and a separate shackle with ward springs. The lock opens in the same way, but the design of this lock is simpler. This type of lock may be the precursor of the padlocks with ward springs that were manufactured in Sweden from the Viking Era and a few centuries afterward.