All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.
Many scholars of Fiqh conditioned for the validity of wiping over the Khuffayn (leather socks) that they should cover the parts (of the feet) that are obligatory to wash in ablution and that they should be firm by themselves on the feet. If they are not firm except by tying them, then it is not valid to wipe over them.
If they are firm by themselves but they need to be tied so that no part of what they must cover is visible, then it is acceptable to wipe over them.
Kashshaaf Al-Qinaa’ reads:
“It is not valid to wipe over leather socks that must be tied to become firm, according to the narration by (Imaam) Ahmad, for what was discussed earlier; and if the leather socks are firm by themselves but they must be tied so that none of the parts that they must cover would be visible, and these parts are not covered except by tying or fastening the leather socks, then it is valid to do so, because they cover the feet and it is possible to continue walking in them, so they are like the ones without fasteners.”
Therefore, if these leather socks are not firm on your feet except by tying them, then do not wipe over them, but if they are firm by themselves – as it appears from the question – but they just need to be fastened with a pin or the like so that the parts that must be washed in ablution are not visible, then there is no harm on you to fasten them with a pin so that these parts would not be visible, and then you wipe over them.
Allah knows best.