Dark Age weaponry is the subject of several books currently in print. The subject has benefited from the popularity of re-enactments, which suggest how the age might have drilled and deployed its armies even when the contemporary record is silent. Facsimile weapons have shed light not only on how Dark Age weapons were used but also on how they were made. Round shields, for example, are four times more effective at resisting missiles when bent into a concave shape. Plain wooden shields, on the other hand, are useless, splintering on the first impact. It is reasonable to suppose that no one used wooden shields without some more effective form of strengthening.