3D Print posted by AlanRichard
The idea of this catch is to enable a sliding chicken hutch (or similar) door to be lifted by a string but to prevent it being pushed up by a fox or other animal.
The string runs through the locking catch and bracket. When pulled, it lifts the catch clear of the lock position.
When the door is pushed up the catch engages as a lock
In my example, it locks onto the wire bar of the weldmesh behind it
It would also work on a smooth surface if you provide an edge to engage the lock.
It would integrate well with an automatic chicken door opener.
I use a length of string on a pully so I can open/ close the inner hutch without going inside an outer compound.
Have lost a few chucks to foxes, it gives some peace of mind that its locked.
For total security the string should be placed behind a screen. A smart fox may figure it eventually.
There is 2 holes through the bracket to screw into a drop door, this was made for a 9mm thick door.
It will need an M4x40 screw and nut for a hinge.
There is a 4mm hole through the width of the catch. I put some M4 stud in there just to add weight to the end to ensure the catch drops down.
It has been in use a while and is reliable.