From PMOG Wiki

Crates allow you to leave PMOG items throughout the web. You can put Data Points (DP), Crates, Mines, Lightposts, St. Nicks, or Armor in a crate.

When you deploy a crate a message is left on the PMOG website. This can work two ways. If you want someone to pick the crate up right away (and perhaps visit the site where you deployed the crate) you can put the crate on the site's main page. If you place the crate within a site (not on the main page) the user might stumble across the crate (passively) or they could go searching the site just for the crate. You should consider this when you deploy your crate.

Benefactors often include crates in crates. If you choose you can use the embedded crate on the same page, with the same or different contents. Using crates will boost your Benefactor rating within PMOG.

If you post a crate on a user's page on pmog.com only the page owner can loot the crate. This is how you leave items for your allies. It is also possible to stash crates on imaginary web pages. This is one way to protect your data points from mines, but of course you have to pay for the crates you use.

http://pmog.com/codex/tools/crates

Notes about the Use of Crates! Crates can only contain 10 total tools. ie all of the tools in the crate together add up to ten, not ten of each.

Crates can only contain a VALUE of 1000 dp. ie you can't add 1000 dp to a crate with tools, it will fail to place and burn up one of your crates.