The best replacement for shackles is blocks.

The best alternatives to shackles are rated as following:
★★★★★  blocks
★★★★★  add a leaf
★★★  aal
★★★  sliders
★★  lift blocks
★  add a leafs
★  zombie world

Your alternative for shackles is not listed? Suggest!
Speaking about shackles, one probably shouldn't forget about flip kit.

Other search terms related to shackles and their ratings are:
★★★★★ flip kit
You have in mind a companion for shackles and it is not yet here? Propose!



Google Trends

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shackles
blocks
add a leaf