Hum ?For Half-Life I think you can make it with, item_security, env_render, func_wall_toggle, multisource, func_door and trigger_auto.
trigger_auto:Target: key_render.
Delay before trigger: 0.5.
Trigger State: Off.
Flags: Remove on fire.
env_render : Name: key_render.
Target: sec_key.
Render Mode: texture.
Fx Amount: 0.
Item_security: Name: sec_key.
Target: M_sec.
Multisource: Name: M_sec.
Target: key.
Func_wall_toggle: Name: key.
Made from a brush, locks as a key.
Func_door: Master: M_sec.
Speed: ...
Sound: ...
Locked Sound: Latch Locked
Trigger_auto start env_render, env_render do item_security invisible, when player pick up the key item_security, item_security activate the multisource and it activate and give func_door master on, multisource do the func_wall_toggle to disappear.
Place item_security and func_wall_toggle on same place.
Can it bi some help? I hop so.