A fish on both flies

[tlspyder13]

Fishing with the tags sounds kind of cool to try. But I have a few questions. If I understand right instead of tying on the first fly you tie to a length of tippet somewhere in the middle or one side longer then the other. You then tie a fly to each of the ends of the leader. What kind of knot do you use to tie onto the tippet and what keeps it from sliding with a fish pulling on only one end of the tippet material?
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