In the UK (and elsewhere?) Lorry tyres have plastic caps on the bolts, with arrows aligned to each other in pairs, or some regular pattern. It's easy to see at

In the UK (and elsewhere?) Lorry tyres have plastic caps on the bolts, with arrows aligned to each other in pairs, or some regular pattern. It's easy to see at a glance if a bolt has loosened. e.g. https://mechanics.stackexchange.com/questions/29690/what-are-the-yellow-triangles-on-truck-wheels-for https://mechanics.stackexchange.com/questions/29690/what-are...