Does the property have the right to detain the goods?

Site security has the right to prevent the goods-pulling vehicles that have entered the site from entering and leaving. This is also his duty.

But this is not to detain the goods. Your understanding is wrong.

If you can issue a certificate according to the regulations, he won't stop you from taking materials from other construction sites.

In other words, if you enter the site, you will first classify and register the materials that are not on site, and then give them to the security guard to explain the situation. Then after you unload the materials to be unloaded, give them to the security guard for verification, and then you can leave with the goods you registered in advance.

In this matter, you should think from other people's point of view. After all, when it comes to commodities, prices and so on, you should also respect your job responsibilities.

But these are not what you call detention. This does not involve "property".