In most Omega maps, crates serve for decorative purpose. However, they don't serve as cover from bullets or grenades, but for meele attacks. There many variants of crates.

Military Crate (often found in EoD_Jail, coop_omega2 and as_vents)

Plated crate (only found in EoD_Jail as breakable crates with the highest durability)
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Top crates

First out of third crates to be breakable (plated crate is excluded). Top crates serve as "walls" and act as a temporary cover. However, in Omega maps, they're quite rare. Top crates are often bright wooden crates.

Large crates

Second out of third crates to be breakable. They have much more durability than on-top crates and explosivecrates. They also have a dirty and old variant which has lesser durability.   
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Explosive crates

Last crate to be breakable. They have the radius of 80 meters and deal 65 damage, depends on proximity. They can be easily recognized by their darkenend crate and their oxidizing hazard symbol.

Tesla gates

Tesla gates aren't considered to be a CS2D obstacle, but rather a custom map obstacle. The tesla gate works in a similiar fashion like the ones in Containment Breach, except that EoD_Jail's tesla gates can be turned off by any person. Tesla gates are recognized by their "bulb floor", dark wall tile, a cyan-flashing light and an idle electric noise. Once an active tesla gate has been passed by a player, a massive tesla shock will be triggered and drain an un-armoured player's hitpoints to 1. It's damage can be reduced by wearing armour.

One tesla gate is located in coop_omega2, but is unactive and cannot be activated due to being implented.  

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Another tesla gate is located in coop_omega10 in a corrupted room. It's button is located on it's right side, making a squad get stuck. Later in the map, an officer requests Control to shut down the tesla gate. If the player returns back, the squad was already gone and a paranoid soldier left a note.